Practice set for BES00002

Question Bank

BRAINWARE UNIVERSITY
Question Bank with Model Answer
Programme – B.Tech.(CSE)-AIML-2024
Course Name – Basic Electrical and Electronics Engineering
Course Code - BES00002
*** Multiple Choice Type Questions ***
1.

(i) Indicate the correct option for the type of electrical device a Transformer is;

a) static (Correct Answer) b) rotating

c) oscillating d) None of these

(ii) Choose the correct option: In a pure inductive circuit

a) b) The current legs behind the voltage by 90 degree (Correct

The current is in phase with the voltage
Answer)
c) The current leads the voltage by 90 degree d) The current can lead or lag by 90 degree

(iii) Identify the law on which the transformer works;

a) Faraday's law of electromagnetic induction (Correct Answer) b) Fleming's right-Hand Rule

c) Fleming's left-hand rule d) None of these

(iv) Identify energy dissipating element from the following:

a) Resistor (Correct Answer) b) Inductor

c) Capacitor d) Both 2 & 3

(v) Choose the unilateral element from following

a) Resistor b) Capacitor
c) Inductor d) Diode (Correct Answer)

(vi) Choose the unit of Resistance from the following:

a) Ohm (Correct Answer) b) Siemens

c) Ohm-meter d) None of these

(vii) Choose the unit of Resistivity from the following:

a) Ohm-meter (Correct Answer) b) Ohm

c) Farad d) Henry

(viii) Identify the material with lots of free electrons from below.

a) Conductors (Correct Answer) b) Insulators

c) Semiconductors d) Filters

(ix) Select the unit of electrical charge from the following:

a) Coulomb (Correct Answer) b) Joule

c) Volt d) Watt

(x) Select from the following, the one that's not a type of energy source:

a) Generator b) Rheostat (Correct Answer)

c) Solar cell d) Battery

(xi) Choose from the following that is measured by a multimeter:

a) Current b) Voltage
c) Resistance d) All of the above (Correct Answer)

(xii) Select the event that occurs as a current through the coil of an electromagnet is reversed

a) direction of the magnetic field remains unchanged b) direction of the magnetic field reverses (Correct Answer)
c) magnetic field expands d) magnetic field collapses

(xiii) Select the power percentage efficiency of supply produced by a 0.6 W output with an input of 0.7 W.

a) 8.57% b) 42.85%
c) 4.28% d) 85.7% (Correct Answer)
 (xiv) A 220 resistor dissipates 3 W. Calculate the voltage.

a) 73.3 V b) 2.5 V
c) 25.7 V (Correct Answer) d) 257 V

(xv) Identify the passive elements

a) Voltage source b) Current source

c) Transistor d) Inductor (Correct Answer)

(xvi) For 12 V and 40 mA, calculate the power in the circuit.

a) 480 mW b) 0.480 W
c) 480,000 µW d) All of them (Correct Answer)

(xvii) State the change occurring due to the reversal of the current through the coil of an electromagnet.

a) direction of the magnetic field reverses (Correct Answer) b) direction of the magnetic field remains unchanged
c) magnetic field expands d) magnetic field collapses

(xviii) Choose the unilateral element from below mentioned option

a) Resistor b) Diode (Correct Answer)

c) Inductor d) Capacitor

(xix) Identify the value of efficiency of a circuit under maximum power transfer condition

a) 0.25 b) 0.5 (Correct Answer)

c) 0.75 d) 0.8

(xx) Thevenin's theorem states that any bilateral network may be swapped out for a network with

a) An independent current source in parallel to the equivalent b) An independent voltage source in series with the equivalent
resistance resistance (Correct Answer)
c) An independent voltage source in parallel to the resistance d) None of these

(xxi) Choose the time period of a sine wave that goes through 10 cycles in 20 s;

a) 20 micro sec b) 4 micro sec

c) 2 micro sec (Correct Answer) d) 100 micro sec

(xxii) Choose the correct option; the peak value divided by the RMS value gives us

a) Peak factor b) Crest factor

c) Both of them (Correct Answer) d) None of peak or crest factor

(xxiii) Identify the term that a phasor represents;

a) the magnitude and a quantity direction (Correct Answer) b) the width of a quantity
c) the phase angle d) the magnitude of a quantity

(xxiv) Identify the correct option: RMS stands for

a) Root Mean Square (Correct Answer) b) Root Mean Sum

c) Root Maximum Sum d) Root Minimum Sum

(xxv) Indicate, Which of the following expressions doesn’t represent the correct formula for Drift current density.

a) J = σE b) J = qnµE
c) J = µE (Correct Answer) d) None

(xxvi) Describe, the tendency of charge carriers to move from a region of heavily concentrated charge to a region of less
concentrated charge is known as:

a) Depletion current b) Drain current

c) Diffusion current (Correct Answer) d) Saturation current

(xxvii) Select, the cut-in voltage of a Ge diode is about

a) 0.2V (Correct Answer) b) 0.6V

c) 0.2mV d) 0.6V

(xxviii) Select the band gap of a semiconductor lies in the range

a) 5 to 10 eV b) 0.2 to 2.5 eV (Correct Answer)

c) 0.01 to 0.1eV d) None of these

(xxix) Identify which of the following atoms can act as donors in Si:

a) As (Correct Answer) b) In
c) Ga d) P

(xxx) Indicate the Fermi level of an n-type semiconductor lies

a) near the conduction band-edge (Correct Answer) b) near the valence band edge
c) at the middle of the forbidden gap d) near the valence band-edge
 (xxxi) Select that a Semiconductor has temperature coefficient of resistance is

a) positive b) zero
c) negative (Correct Answer) d) None of these

(xxxii) Identify that addition of pentavalent impurity to a semiconductor creates many

a) free electrons (Correct Answer) b) holes

c) valence electrons d) bound electrons

(xxxiii) Interpret that in an intrinsic semiconductor, the number of free electrons

a) equals the number of holes (Correct Answer) b) is greater than the number of holes
c) is less than the number of holes d) None of these

(xxxiv) Select that at absolute zero temperature, an intrinsic semiconductor has

a) a few free electrons b) many holes

c) many free electrons d) no holes or free electrons (Correct Answer)

(xxxv) Indicate the band gaps of silicon and germanium are

a) 0.67 eV and 1.1 eV (Correct Answer) b) 0.87 eV and 6.78 eV

c) 5.89 eV and 4.6 eV d) 0.54 eV and 0.7861 eV

(xxxvi) Select that the acceptor impurities

a) generate electrons b) generate holes (Correct Answer)

c) generate holes and electrons d) None of these

(xxxvii) Recall that in an intrinsic semiconductor, the Fermi level lies

a) above the centre of the energy gap b) below the centre of the energy gap
c) in the middle of the energy gap (Correct Answer) d) anywhere in the energy gap

(xxxviii) Choose that at 0 K an intrinsic semiconductor behaves as a/an

a) conductor b) insulator (Correct Answer)

c) semiconductor d) any of the above

(xxxix) State that the process of adding impurities to an intrinsic semiconductor is called

a) annealing b) etching
c) doping (Correct Answer) d) alloying

(xl) State the electric field between acceptor and donor ions in a PN junction with no external voltage.

a) Peak b) Barrier (Correct Answer)

c) Threshold d) Path

(xli) Identify the correct option for an PN junction diode.

a) Has low resistance in forward as well as reverse directions b) Has high resistance in forward as well as reverse directions
c) Conductors in the forward direction only (Correct Answer) d) Conducts in the reverse direction only

(xlii) Enumerate the biasing conditions for the PN junction diode.

a) One b) Two
c) Three (Correct Answer) d) Four

(xliii) Identify the doping level associated with Zener breakdown in a Zener diode.

a) Lowest b) Moderate
c) High (Correct Answer) d) Low

(xliv) Define the purpose of a rectifier.

a) Convert ac voltage to dc voltage (Correct Answer) b) Convert dc voltage to ac voltage

c) Measure resistance d) Measure current

(xlv) State the ripple factor for a half-wave rectifier.

a) 2 b) 1.21 (Correct Answer)

c) 0.482 d) 0.877

(xlvi) Define the form factor for a full-wave rectifier.

a) 1.11 (Correct Answer) b) 1.57

c) 2.62 d) 0.453

(xlvii) State the transformer utilization factor of a bridge full-wave rectifier.

a) 0.623 b) 0.812 (Correct Answer)

c) 0.692 d) 0.825

(xlviii) State what the Peak Inverse Voltage (PIV) of a half-wave or full-wave rectifier always is.
 a) Greater than the input voltage b) Smaller than the input voltage (Correct Answer)
c) d) Greater than the input voltage for full wave rectifier and
Equal to the input voltage
smaller for the half wave rectifier

(xlix) Identify the correct option when a PN junction is said to be forward biased.

a) Positive terminal of the battery is connected to P-side and the b)

Junction is earthed
negative side to the N-side (Correct Answer)
c) d) Positive terminal of the battery is connected to N-side and the
N-side is connected directly to the p-side
negative side to the P-side

(l) Indicate the results of testing a good diode with an ohmmeter.

a) high resistance when forward or reverse biased b) low resistance when forward or reverse biased
c) high resistance when reverse biased and low resistance when d) high resistance when forward biased and low resistance when
forward biased (Correct Answer) reverse biased

(li) Indicate the function of a zener diode.

a) half wave regulator b) half wave rectifier

c) voltage regulator (Correct Answer) d) amplifier

(lii) Indicate the function of filter circuits after rectifiers.

a) smoothens pulsation (Correct Answer) b) hardens pulsation

c) keeps the pulsation as it is d) doubles the pulsations

(liii) Select the function that is most applicable for a voltage regulator circuit.

a) Converts the DC voltage into AC voltage. b) Converts the AC voltage into DC voltage.
c) d) Maintains a constant DC output voltage in spite of the
Smoothens the AC variations in DC output voltage. fluctuations in AC input voltage or load current. (Correct
Answer)

(liv) Identify the equation used to describe the static VI characteristics of a junction diode.

a) Child\'s three half-power law b) Boltzmann diode equation (Correct Answer)

c) Einstein\'s photoelectric equation d) Richardson-Dushman equation

(lv) Identify the basic purpose of a filter.

a) minimize variations in ac input signal b) suppress harmonics in rectified output

c) remove ripples from the rectified output (Correct Answer) d) stabilize dc output voltage

(lvi) Predict how modified the ripple factor is in an LC filter.

a) Increases with the load current b) increases with the load resistance
c) remains constant with the load current (Correct Answer) d) has the lowest value

(lvii) Indicate how dynamic resistance is calculated.

a) ∆I / ∆V b) V / I
c) I / V d) ∆V / ∆I (Correct Answer)

(lviii) Predict the appropriate one, which causes avalanche breakdown.

a) b) The high electric field creating a chain reaction of electron

Tunnelling of electrons across the junction
collisions (Correct Answer)
c) Thermal energy d) Diffusion of carriers

(lix) Determine what happens to dynamic resistance if the slope of the I-V characteristic curve is steep.

a) It increases b) It decreases (Correct Answer)

c) It remains the same d) It becomes zero

(lx) Determine the value of peak reverse voltage (P.I.V.) if the full-wave rectifier has an alternating voltage of 300 V.

a) 849 V (Correct Answer) b) 800 V

c) 750 V d) 870 V

(lxi) Determine the ripple frequency of a bridge full-wave rectifier if the input frequency is 50 Hz.

a) 45Hz b) 50Hz
c) 100Hz (Correct Answer) d) 200Hz

(lxii) Calculate the total current in the semiconductor diode if the drift current is 100 mA and the diffusion current is 1 A.

a) 1.01 A b) 1.1 A (Correct Answer)

c) 900 mA d) 10 A

(lxiii) Compute the DC load current for a full-wave rectifier with a load resistance of 5 kΩ, an inductor filter of 15 henry, a
peak applied voltage of 250 V, and a frequency of 50 cycles per second.

a) 0.7 mA b) 17 mA
c) 10.6 mA (Correct Answer) d) 20 mA
 (lxiv) Determine the DC output voltage of a single-phase full-wave rectifier with a pi-section filter using 10 µF capacitors and
a 10 henry choke, a secondary voltage of 280 V, and a load current of 100 mA when the frequency is 50 Hz.

a) 243 V b) 345 V
c) 346 V (Correct Answer) d) 521 V

(lxv) Calculate the ripple factor for a CLC filter with an operating frequency of 50 Hz, 10 µF capacitors, a load resistance of
3460 Ω, and an inductance of 10 henry.

a) 0.00142 b) 0.00165 (Correct Answer)

c) 0.00178 d) 0.00321

(lxvi) Calculate the current when a forward potential of 10V is applied to a Si diode in series with a 1 kΩ resistor.

a) 10 mA b) 9.3 mA (Correct Answer)

c) 0.7 mA d) 0 mA

(lxvii) Calculate the barrier potential at 125°C, given that it is 0.7V at room temperature (25°C).

a) 0.5 V (Correct Answer) b) 0.3 V

c) 0.9 V d) 0.7 V

(lxviii) Calculate the maximum voltage across each reverse-biased diode in a bridge-type full-wave rectifier, given that 𝑉𝑚 is
the peak voltage across the secondary of the transformer.

a) Vm (Correct Answer) b) 2 Vm
c) Vm/2 d) Vm/√2

(lxix) Identify the power factor of an ordinary electric bulb;

a) zero b) unity
c) more than unity d) less than unity (Correct Answer)

(lxx) Select the unit of reactive power;

a) VA b) Watt
c) VAR (Correct Answer) d) Ohm

(lxxi) Select the Unit of inductive reactance;

a) Henry b) mili-Henry
c) Weber d) Ohm (Correct Answer)

(lxxii) Cite the identity of a pure inductive circuit;

a) Active power is zero (Correct Answer) b) Reactive power is zero

c) Apparent power is zero d) None of these

(lxxiii) Choose the value that comes on dividing peak value by the RMS value;

a) Peak factor b) Crest factor

c) Both of these (Correct Answer) d) None of these

(lxxiv) Identify the unit of frequency is;

a) Cycle b) Hertz (Correct Answer)

c) Cycle-second d) Hertz/second

(lxxv) Choose from the following the law on which KCL is based:

a) Law of conservation of charge (Correct Answer) b) Law of conservation of energy

c) Law of conservation of mass d) None of these

(lxxvi) Choose from the following the law on which KVL is based:

a) Law of conservation of energy (Correct Answer) b) Law of conservation of charge

c) Law of conservation of mass d) None of these

(lxxvii) Recognize how the location of the Zener region can be controlled in the diode characteristic curve.

a) b) By changing the doping concentration of the diode (Correct

By changing the value of Iz
Answer)
c) By changing the operating temperature d) By increasing the size of diode

(lxxviii) Choose the correct option. For a star-connected three-phase AC circuit;

a) Phase voltage is equal to line voltage, and phase current is b) Phase voltage is square root three times line voltage, and
three times the line current. phase current is equal to line current. (Correct Answer)
c) Phase voltage is equal to line voltage and line current is equal d)
None of these.
to phase current.

(lxxix) Choose the correct option. In a three-phase delta connection;

a) Line current is equal to phase current. b) Line voltage is equal to phase voltage. (Correct Answer)
c) Line voltage and line current are zero. d) None of these.
 (lxxx) Identify which of the following is kept fixed in a transformer;

a) Voltage b) Current
c) Frequency (Correct Answer) d) None of these

(lxxxi) Identify the way by which the windings of a transformer are coupled;

a) Electrically b) Magnetically (Correct Answer)

c) Either electrically or magnetically d) None of either options

(lxxxii) Identify a pure inductive circuit;

a) Actual power is zero. (Correct Answer) b) Reactive power is zero

c) Apparent power is zero d) None of these

(lxxxiii) Identify the unit of inductive reactance from the following:

a) Ohm (Correct Answer) b) Mho

c) Siemens d) Ohm-meter

(lxxxiv) Identify the unit of capacitive reactance from the following:

a) Ohm (Correct Answer) b) Mho

c) Siemens d) Ohm-meter

(lxxxv) Identify the correct statement for KCL:

a) At a node, the sum of incoming current equals the sum of b)

at a node, the algebraic sum of the currents are zero
outgoing current.
c) at a node, sum of incoming current > sum of outgoing current d) both 1 and 2 (Correct Answer)

(lxxxvi) The time period of a sine wave is 0.04 sec. Choose the value of frequency:

a) 50 b) 25 (Correct Answer)
c) 5 d) 2.5

(lxxxvii) Cite the particular DC motor that cannot be started with 'no-load'.

a) Shunt motor b) Separately excited motor

c) DC series motor (Correct Answer) d) Both 1 and 2

(lxxxviii) Estimate the reason for laminating the core of a transformer or a three-phase induction motor is to reduce;

a) Copper loss b) Eddy current loss (Correct Answer)

c) Both of these d) None of these

(lxxxix) Select the value of percentage of slip of a three-phase induction motor at starting;

a) 0.5 b) 1 (Correct Answer)

c) 1.5 d) 2

(xc) Select the reason for starter in the DC motor.

a) To limit high starting current (Correct Answer) b) To limit the starting speed
c) Both 1 and 2 d) None of these

(xci) Select from following the parameter kept fixed in a transformer;

a) voltage b) current
c) frequency (Correct Answer) d) None of these

(xcii) Recognize the way to couple the windings of a transformer;

a) Magnetically (Correct Answer) b) Electrically

c) Either magnetically or electrically d) Neither magnetically no electrically

(xciii) A transformer has voltage rating of 220/110 volt. Interpret the correct option;

a) Step-up b) Step-down (Correct Answer)

c) Isolation d) All of these

(xciv) Select the function of a transformer;

a) To step down or up the AC voltages and currents (Correct b)

To step down or up the DC voltages and currents
Answer)
c) Converts DC to AC voltages d) Converts AC to DC voltages

(xcv) Select the value of transformation ratio of step-up transformer;

a) zero b) greater than 1 (Correct Answer)

c) less than 1 d) equal to 1

(xcvi) Select the type of loss which is not present in the transformer;

a) Core loss b) Copper loss

c) Windage loss (Correct Answer) d) None of these
(xcvii) Choose the rating of transformer;

a) KVA (Correct Answer) b) KW

c) HP d) KVAR

(xcviii) Identify the type of flux generated in a transformer;

a) DC supply b) AC supply (Correct Answer)

c) Both of these d) None of these

(xcix) Choose the value of frictional loss in a transformer;

a) zero (Correct Answer) b) one

c) infinity d) none

(c) Using a two-wattmeter method with identical values, choose the power factor in a three-phase power measurement;

a) Unity (Correct Answer) b) 0.8 leading

c) 0.8 lagging d) Zero

(ci) Identify the electric power in a three-phase Phase Circuit;

a) P = 3 VPh IPh CosФ b) P = √3 VL IL CosФ

c) Both of these (Correct Answer) d) None of these

(cii) Calculate the peak value of a sine wave if the RMS value is 100 A.

a) 70.7A b) 141A (Correct Answer)

c) 150A d) 282.8A

(ciii) Choose the appropriate choice for the material that the induction motor shaft is composed of.

a) Mild steel (Correct Answer) b) Cast iron

c) High-speed steel d) Stainless steel

(civ) Predict the right choice. Laminating the stator core of a three-phase induction motor lowers the

a) Eddy current loss (Correct Answer) b) Hysteresis loss

c) Both of these d) Weight of the stator

(cv) Identify the right one. The operation of an induction motor is

a) DC only b) AC only (Correct Answer)

c) Both of these d) None of these

(cvi) Identify the shape of carbon brushes in a DC machine;

a) Triangular b) Square (Correct Answer)

c) Cylindrical d) Semi-circular

(cvii) Identify the condition for maximum efficiency in a transformer;

a) core loss>copper loss b) core loss = copper loss (Correct Answer)

c) core loss<copper loss d) None of these

(cviii) Select the correct option. In a 3-phase squirrel cage induction motor;

a) Rotor conductors are short circuited through end rings b)

Rotor conductor ends are short circuited through slip rings
(Correct Answer)
c) Rotor conductors are kept open d) None of these

(cix) Select the value of synchronous speed of a three phase induction motor with 4 pole and supply frequency of 50 Hz.

a) 3000 rpm b) 2500 rpm (Correct Answer)

c) 2000 rpm d) 1500 rpm

(cx) Select the no-load speed of the following DC motor that will be highest.

a) Shunt motor b) Series motor (Correct Answer)

c) Cumulative compound motor d) Differentially compound motor

(cxi) State the reason for starter in the DC motor.

a) To limit high starting current (Correct Answer) b) To limit starting speed

c) Both 1 & 2 d) None of these

(cxii) Select the type of loss that is not present in the transformer.

a) Core loss b) Copper loss

c) Windage loss (Correct Answer) d) None of these

(cxiii) The short-circuit test is conducted in a transformer to estimate the

a) Core loss b) Copper loss (Correct Answer)

c) Both of these d) None of these

(cxiv) The open-circuit test is conducted in a transformer to estimate the

 a) Core loss (Correct Answer) b) Copper loss
c) Both 1 & 2 d) None of these

(cxv) Select the purpose of the transformer core;

a) To provide low-reluctance path (Correct Answer) b) To provide high reluctance path

c) To provide low capacitive path d) To provide high capacitive path

(cxvi) Interpret the situation if the secondary of a current transformer is open-circuited;

a) depends on other parameters b) cool as there is no secondary current

c) hot because primary will carry heavy current d) hot because of heavy iron losses (Correct Answer)

(cxvii) Select the amount of total power that is transferred inductively for a 20kVA transformer with a turn ratio of 0.4;

a) 10 kVA b) 8 kVA
c) 50 kVA d) 12 kVA (Correct Answer)

(cxviii) Indicate the correct option of the variable loss in a transformer;

a) Eddy current loss b) Hysteresis loss

c) Copper loss (Correct Answer) d) Both eddy current & hysteresis loss

(cxix) An AC voltage is applied across a pure inductor. Identify the correct statement;

a) voltage leads current by 90 degrees (Correct Answer) b) current leads voltage by 90 degrees
c) current and voltage are in phase d) current lags voltage by an angle less than 90 degrees

(cxx) The self-inductance of a coil is 10 H. Choose the value of inductive reactance at 50 Hz from the following:

a) 3140 W (Correct Answer) b) 314 W

c) 31.4 W d) 3.14 W

(cxxi) A sine wave has a frequency of 50 Hz. Indicate the value of angular frequency;

a) 31.4 rad/s b) 314 rad/s (Correct Answer)

c) 3.14 rad/s d) None of these

(cxxii) If current in a circuit is given by i=10 sin 314t, then estimate the RMS value of current.

a) 70.7 A b) 6.37 A
c) 7.07 A (Correct Answer) d) 5.23 A

(cxxiii) The active power consumed by a circuit is 120 W, while the apparent power consumed is 200 W. Select the value of the
power factor.

a) 0.8 b) 0.6 (Correct Answer)

c) 0.5 d) 0.9

(cxxiv) Identify that, in an NPN transistor, the arrow is pointed towards

a) the collector b) the base

c) depends on the configuration d) the emitter (Correct Answer)

(cxxv) In the operation of an NPN transistor, indicate the region that electrons can cross:

a) emitter region b) the region where there is high depletion

c) the region where there is low depletion d) P type base region (Correct Answer)

(cxxvi) Illustrate which of the following are true for a PNP transistor.

a) the emitter current is less than the collector current b) the collector current is less than the emitter current
c) the collector current is less than the emitter (Correct d)
the holes are the minority charge carriers
Answer)

(cxxvii) Identify the type of amplifiers exhibit the current gain approximately equal to unity without any current amplification.

a) CE b) CC (Correct Answer)
c) CB d) None of these

(cxxviii) Indicate the true statement of the following

a) CC amplifier has a large current gain b) CE amplifier has a large current gain (Correct Answer)
c) CB amplifier has low voltage gain d) CC amplifier has low current gain

(cxxix) Identify the doped region in a transistor are ________

a) Emitter and Collector b) Emitter and Base

c) Collector and Base d) Emitter, Collector and Base (Correct Answer)

(cxxx) Indicate highly doped region of the transistor is

a) Emitter (Correct Answer) b) Base

c) Collector d) Both Emitter and Collector

(cxxxi) Illustrate the term BJT is

 a) Bi-Junction Transfer b) Blue Junction Transistor
c) Bipolar Junction Transistor (Correct Answer) d) Base Junction Transistor

(cxxxii) Identify the junction that is forward biased when transistor is used as an amplifier

a) Emitter-Base (Correct Answer) b) Emitter-Collector

c) Collector-Base d) No junction is forward biased

(cxxxiii) Illustrate that in the active region the emitter-base junction is _______ biased and base-collector junction is ________
biased

a) Reversed biased, Forward biased b) Forward biased, Forward biased

c) Reversed biased, Reversed biased d) Forward biased, Reverse biased (Correct Answer)

(cxxxiv) Due to forward biasing of emitter-base junction, indicate ________ are induced into the base

a) Minority carriers b) Majority carriers (Correct Answer)

c) All the charge carriers d) Only electrons.

(cxxxv) Identify the element that has the biggest size in a transistor is

a) Collector (Correct Answer) b) Base

c) Emitter d) Collector-base junction

(cxxxvi) Determine the collector of a transistor is _______ doped.

a) heavily b) moderately (Correct Answer)

c) lightly d) none of these

(cxxxvii) Determine a transistor is ________ operated device.

a) current (Correct Answer) b) voltage

c) both voltage and current d) none of these

(cxxxviii) Determine that most of the majority carriers from the emitter

a) recombine in the base b) recombine in the emitter

c) pass through the base region to the collector (Correct d)
none of these
Answer)

(cxxxix) Express that in a transistor

a) IC = IE IB b) IB = IC IE
c) IE = IC − IB d) IE = IC IB (Correct Answer)

(cxl) Choose the value of α of a transistor is

a) more than 1 b) less than 1 (Correct Answer)

c) 1 d) none of these

(cxli) Determine the output impedance of a transistor is

a) high (Correct Answer) b) zero

c) low d) very low

(cxlii) In a transistor, IC = 100 mA and IE = 100.5 mA. Calculate the value of β is

a) 100 b) 50
c) about 1 d) 200 (Correct Answer)

(cxliii) Compare the relation between β and α is

a) β=1/(1-α) b) β=1/(1 α)
c) β=α /(1-α) (Correct Answer) d) β=α /(1 α)

(cxliv) Identify the most commonly used transistor arrangement is

a) common emitter (Correct Answer) b) common base

c) common collector d) none of these

(cxlv) For a certain transistor, IB = 20 microA; IC = 2 mA and beta= 80.Estimate ICEO.

a) 0.4 mA (Correct Answer) b) 0.8 mA

c) 1.2 mA d) 1 mA

(cxlvi) Estimate the collector current for a C-E configuration with a beta of 100 and a base current of 30 microA?

a) 30 microA b) 0.3 microA

c) 3mA (Correct Answer) d) 3A

(cxlvii) Illustrate, a collector characteristic curve is a graph showing:

a) emitter current (IE) versus collector-emitter voltage (VCE) b) collector current (IC) versus collector-emitter voltage (VCE)
with (VBB) base bias voltage held constant with (VBB) base bias voltage held constant (Correct Answer)
 c) collector current (IC) versus collector-emitter voltage (VC) d) collector current (IC) versus collector-emitter voltage (VCC)
with (VBB) base bias voltage held constant with (VBB) base bias voltage held constant

(cxlviii) Illustrate the ratio of collector current by the base current is known as _______________ gain

a) Current (Correct Answer) b) Voltage

c) Efficiency d) None of these

(cxlix) Recall that the gate voltage in a JFET at which drain current becomes zero is called:

a) saturation voltage b) pinch-off voltage (Correct Answer)

c) active voltage d) cut-off voltage

(cl) Select that in a JFET the IDSS is known as:

a) drain to source current b) drain to source current with gate shorted (Correct Answer)
c) drain to source current with gate open d) none of these

(cli) Select that a JFET is called _____________ transister.

a) unipolar (Correct Answer) b) bipolar

c) uni junction d) none of these

(clii) Identify that a JFET is a _________________ driven device.

a) current b) voltage (Correct Answer)

c) both current and voltage d) none of these

(cliii) Identify that if the reverse bias on the gate of a JFET increased, then width of the conducting channel
_________________ .

a) is decreased (Correct Answer) b) is increased

c) remains the same d) none of these

*** Short Answer Type Questions ***

2. An alternating voltage is given by the equation v = 200 sin (377t + π/5). Calculate rms value, frequency and the time period.
Answer: Vm = 200 V. Thus, Vrms = 0.707x200 = 141.4 V., ω = 2πf=377 rad/s, f = 377/2π = 60 Hz. T=1/f = 0.0167 s.

3. Compute the terms peak factor and form factor of a AC wave. What are their values for a sinusoidal AC wave?
Answer: Peak factor is defined as the ratio of peak or maximum value of an alternating quantity to its rms value. For a sinusoidal wave Ka = Im/Irms = 1.414.
sinusoidal wave, Kf = Irms/Iav = 1.11.

4. A circuit consists of a capacitor of 300 micro F alone connected across an alternating voltage of v=100 sin 100πt. Express the expression for current.
Answer: C = 300 micro F. Thus, XC = 1/ωC = 10.61 ohm. Thus, iC = Vm/Xc sin(100 π t + π /2) = 100/10.61 sin(100 π t + π /2) = 9.425sin(100 π t + π /2).

5. When a certain inductive coil is connected to a DC supply at 200 V, the current in the coil is 10 A. When the same coil is connected to an ac supply at 200 V, 5
Answer: For DC, the reactance of the coil is zero (as f=0). Thus, resistance of the coil = 200/10 = 20 ohms. For ac supply, impedance=200/8 = 25 ohms. Thus, r

6.

Calculate the current supplied by the battery in the given circuit.

Answer: Req = 8 x16/24 = 16/3. Thus, I = 48/16/3 = 9 A

7.

Calculate the current through each resistor.

Answer: I = 200/(20 + 25 + 55) = 2 A.

8. Describe the construction of three phase induction motor.

Answer: The construction of three phase induction motor can be classified in two classes i.e. Stator and rotor. The core of the stator and rotor are made of m
Again the core is made of laminations to reduce the eddy current loss. In the inner periphery of the stator core, the three phase stator winding is wound whose thre
is the rotating part of the motor. The rotor winding is of two types, i.e. Squirrel cage type and wound rotor type. The squrrel cage type rotor is made of rotor bar
winding is a three phase winding whose three terminals are ended at the three slip rings. Thus, the wound rotor type three phase induction motor is having the
torque as well as smooth speed control.
9. Describe the working principle of three phase induction motor.
Answer: When the primary winding or stator is connected to a 3 phase A.C. supply, it establishes a rotating magnetic field which rotates at a synchronous sp
the order in which these lines are connected to the stator. Thus, interchanging the connection of any two primary terminals to the supply will reverse the directi
synchronous speed of rotation in the motor’s stator. Motors are commonly configured to have 2, 4, 6 or 8 poles. The synchronous speed, a term given to the spe
expression. Ns=(120f/P) where, Ns=synchronous speed, f=supply frequency, P= No. of pole. A rotating magnetic field in the stator is the first part of the operation
motors, this current comes from the rotor conductors. The revolving magnetic field produced in the stator cuts across the conductive bars of the rotor and indu
through an external resistance or directly shorted. Therefore, the EMF induced in the rotor causes current to flow in a direction opposite to that of the revolving mag

10. Explain the torque slip characteristic of three phase induction motor.
Answer: Torque-slip characteristics give the relation between torque and slip. The torque-slip characteristics show how the torque changes with a change i
actual speed of the rotor varies with loading condition. Therefore, the slip changes with loading condition. T=k(sR(E^2))/((R^2)+((sX)^2)).Low slip region, High slip
T=ks hence the curve is linear in nature

11. Explain the need for a starter in a DC motor.

Answer: " For DC motors, Voltage equation is, V=Eb-IaRa, Where V = Terminal voltage, Eb = Back emf in Motor, Ia = Armature current, Ra = Aramture resistan
will become enormously increased. The excessive current will damage commutator and brushes and eventually blow out the fuses."

12. Explain back emf of of a DC motor.

Answer: When the armature of a d.c. motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field an
to the applied voltage V (Lenz’s law) and in known as back or counter e.m.f Eb. It is always less than the applied voltage V, although this difference is small when the

13. If a 4 pole lap wound DC shunt motor is having the input voltage of 15 V and armature resistance of 1 Ohm. Calculate the value of armature current. When t
conductors is 80.
Answer: Eb=(P*Phi*Z*N)/(60*A), where Eb=back emf, P=No. of pole, Phi=flux per pole in Wb(m^(-2)), Z= total no. of conductors, N=speed in rpm, A= no. of
Vin=15 V, Armature current= (V-Eb)/Ra=(15-13.33)/1=1.66A

14. A single phase transformer has 500 primary and 1000 secondary turns. The net cross sectional area of the core is 50 cm2. If the primary winding is connecte
Answer: V1 = 4.44 x phi_m x f x N1. Thus, phi_m = 400/50 x 4.44 x 500 = 3.6 x 10^-3. Bm = 3.6 x 10^-3/50 x 10^ (-4) = 0.72 Wb/m^2

15.

Explain the construction

of core type transformer.

Answer: <table border="0" cellpadding="0" cellspacing="0" width="242" style="border-collapse: collapse;width:182pt"> <tbody> <tr height="20" style="
core type construction of the transformer, the magnetic core consists of two vertical lags called limbs and two horizontal sections called yokes. In order to reduce th
low voltage (lv) winding is placed next to the core and the high voltage (hv) winding is placed around the low voltage winding. This reduces the requirement of insula
known as concentric winding or cylindrical winding. The core type construction of transformer is easier to dismantle for maintenance. The natural cooling is good i
small output applications.</td> </tr> </tbody> </table>

16. Identify the reason behind the transformer rating in KVA.

Answer: Any transformer introduces core losses and copper losses.Core losses are dependent on the input voltage. Copper losses are dependent on the curr
not upon power factor. Thus, the rating of the transformer is done in kVA, not in kW.

17. Calculate the magnetizing and core loss component of currents, if no load current (I0)=1A, and no load power factor is 0.2.
Answer: "Im= I0sinø =0.96A Ic=I0cosø=0.2A "

18. Explain the KCL and KVL.

Answer: KCL states that in an electrical circuit, at a node, the total current entering the node is equal to total current leaving the node. KVL states that in any

19. Explain the steps of Norton's theorem for finding the current through load resistance.
Answer: 1) Remove the load resistance. 2) Replace by short circuit. 3) Calculate the current flowing through the short circuit (IN). This is called Norton\'s eq
resistances and find the equivalent resistance of the circuit as seen from the open terminals. This is called Norton\'s equivalent resistance (RN). 5) Draw the Norton
calculate the load current using current division rule

20. A sine wave has a frequency 50 Hz, rms volage is 30V. Construct the equation of voltage.
Answer: Vrms = 30 V. Thus, Vm = 1.414 x 30 = 42.42 V. Thus equation of voltage = 42.42 sin 2 x 3.14 x 50 x t = 42.42 sin 314t

21. Explain superposition theorem.

Answer: If two or more voltage or current sources are acting simultaneously in a linear network, the resultant current in any branch is the algebraic s
independent sources are replaced by their internal resistances.

22. Explain reason of making the terminals of current sources are open ciruited and the terminals of voltage source is short circuited during the execution of the
Answer: Both the sources replaced by its internal resistance... Voltage source have internal resistance equal to zero,hence it replaced by short circuit. While
open circuit.

23. Explain in brief Norton's theorem.

Answer: Norton’s theorem states that any 2-terminal linear and bilateral network or circuit having multiple independent and dependent sources can be
equivalent circuit consists of Norton’s current source, IN in parallel with Norton’s resistance, RN.
24. State the current division rule.
Answer: Current flowing through a resistance = Total resistance x opposite resistance / summation of the two resistances

25. State the types of EMF sources.

Answer: At first the EMF sources are classified in two classes i.e. Independent source and dependent source. The independent source is of two types i.e., Ind
types viz. Voltage dependent voltage source, Current dependent voltage source, Voltage dependent current source, Current dependent current source.

26. Define cycle, frequency and time period of an AC waveform

Answer: Cycle is defined as a complete set of positive and negative values of an AC quantity. Time period isdefined as the time taken by an alternating qua
seacond by an alternating quantity is known as frequency. it is expressed in Hertz.

27. Write one example each of linear element, non linear element.
Answer: Example of linear element is resistor. Example of non-linear element is transistor. Example of unilateral element is diode.

28. Explain the terms peak factor and form factor of a AC wave. What is their values for a sinusoidal AC wave?
Answer: Peak factor is defined as the ratio of peak or maximum value of an alternating quantity to its rms value. For a sinusoidal wave Ka = Im/Irms = 1.414.
sinusoidal wave, Kf = Irms/Iav = 1.11.

29. Explain the terms phase sequence, line voltage and phase current in relation to three phase circuits
Answer: Phase sequence is defined as the sequence in which the three voltages or currents in a three phase system attain their maximum values. The pot
called line voltage. The current flowing through any phase in a three phase circuit is called phase current.

30. State the units of active power, reactive power and apparent power
Answer: Unit of active power: watts (W), unit of reactive power: volt -ampere reactive (VAR), unit of apparent power: volt-ampere (VA).

31. Consider a phase sequence R-Y-B. Considering R phase as the reference, write the voltage equation for the three phases.
Answer: Let Vm be the maximum voltage of each phase. Let ω be the angular frequency. Thus with R phase as the reference at any time t, the ltage equation

32. Distinguish between Electric and Magnetic circuits.

Answer: Electric circuits provide a closed path for the flow of electric current whereas magnetic circuits provide a closed path for the flow of magnetic fl
circuits magnetomotive force (MMF) acts as the driving force.Electric current flows through electric circuits whereas magnetic flux flows through magnetic circuits.Re
flow of magnetic flux in magnetic circuits.Kirchhoff\'s voltage and current laws govern electric circuits whereas Kirchhoff\'s MMF and flux laws govern magnetic circ
static flux in magnetic circuits.Free electrons flow in electric circuit loops while aligned molecular poles generate static flux in magnetic circuits.

33. Illustrate the analogy between Electric and Magnetic circuits

Answer: The analogies between electric and magnetic circuits are two: the electric circuit quantity of current is analogous to magnetic circuit quantity flux. (
circuit quantity of voltage, or electomotive force (EMF) is analogous to the magnetic circuit quantity of magnetomotive force (MMF). EMF is the integral of electric fie

34. Describe the difference between node and junction in an electric circuit.
Answer: Node: The point in a network at which two or more circuit elements are joined. Junction: The point in a network at which three or more circuit elem

35. Describe the Linear and nonlinear circuit with examples.

Answer: The circuit with linear V-I characteristic is called as inear circuit. Ex. Resistive circuit. The circuit having nonlinear V-I characteristic is termed as non-li

36. Describe the bilateral and unilateral circuit with examples.

Answer: The circuit which can allow the flow of current in either directions without changing the property of the elements is called bilateral circuit. Ex. R
changing the property of the elements and only unidirectional flow of current is allowed is called unilateral circuit. Ex. Diode circuit.

37. Describe the active and passive elements in a circuit.

Answer: Active element: The element in a network which can provide the energy to the circuit. (Ex. Voltage and current sources). Passive element: The e
Capacitor).

38.
Calculate the electrical conductivity of an intrinsic silicon semiconductor at 300 K. The mobility of electrons (µn) is 1350 cm2/V. s and the mobility of the holes (µp) is


Answer:
39. Explain the phenomenon of diffusion of current carriers in a semiconductor

Answer:

40. Estimate the conductivity and resistivity of pure Ge at 300K. Assume that at 300K intrinsic carrier concentration is 2.5x 1019m-3, electron mobility=0

Answer:
41. Establish the relationship between mobility and current density for a semiconductor.

Answer:

42. Establish the relationship between conductivity and current density for a semiconductor.

Answer:
43. Explain the construction of transistor with diagram.

Answer:

44. Illustrate Dynamic Input and Output Resistance and current gain in CB mode operation.

Answer:
45. Explain three terminals of a transistor.

Answer:

46. Identify the advantages and disadvantages of Transistor.

Answer:
47. Differentiate among Active region, Cut-off region and Saturation region at CB mode.

Answer:

48. Deduce the relation between β and α.

Answer:
49. In a common base connection, current amplification factor is 0.9. If the emitter current is 1mA, determine the value of base current.

Answer:
50. A half-wave rectifier is used to supply 50 volts DC to a resistive load of 800 Ω. The diode has a resistance of 25 Ω. Calculate the AC voltage required.

Answer:

51. Compare avalanche breakdown and zener breakdown.

Answer:
52. Describe the formation of a barrier field across a p-n junction diode.

Answer:

53. Compare a half-wave and a full-wave rectifier.

Answer:
54. Represent the mathematical expression for the RMS value of the half-wave rectified cycle.

Answer:

55. Illustrate about the rectification efficiency of the half-wave Rectifier.

Answer:
56. Describe the working of the p-n junction diode under forward and reverse bias conditions and state Schokley's equation.

Answer:

57. Describe the operation of a bridge rectifier circuit with a diagram.

 Answer:

58. A center tap full wave rectifier supplies a load of 1 KΩ. The AC voltage across the secondary is 220 (RMS). If diode resistance is neglected, calculate t

Answer:

59. Describe the operation of the zener diode as a voltage regulator.

Answer:
60. Explain what are the applications of junction field effect transistors?

Answer:

The JFET is widely used in different applications due to its extraordinary features. Some of them are:

The junction field effect transistor (JFET) can be used as a switch, a chopper, or a buffer.
The JFET is used in oscillatory circuits and cascade amplifiers.
It can be used as a voltage control resistor, a high input impedance amplifier, a differential amplifier, a low noise amplifier, and a constant current source.

61. Illustrate that what do you understand by pinch off voltage ?

Answer:

As the reverse bias is further increased, the effective width of the channel decreases, the depletion region or the space charge region wi
the source to drain. Finally at a certain gate to source voltage VGS = VP.

*** Long Answer Type Questions ***

62. Explain the Armature control method in DC motors
Answer: Speed of a dc motor is directly proportional to the back emf Eb and Eb = V - IaRa. That means, when supply voltage V and the armature resist
if we add resistance in series with the armature, Ia decreases and, hence, the speed also decreases. Greater the resistance in series with the armatur

63. Explain the Field control of DC motor.

Answer: Field control is a common method used to control the speed of a DC motor. In this method, the speed of the motor can be varied by cha
**Armature Circuit Dynamics**: The armature circuit includes the armature winding and a connected resistor. The voltage applied to the armatu
circuit, comprising the field winding and a field resistor, controls the strength of the magnetic field in the motor. The field current influences the mo
the motor, such as the rotor’s inertia and damping factors, introduce inertia and friction effects that impact the motor’s acceleration and deceler
adjustment of a DC series motor by armature control may be done by the Armature Resistance Control Method, Shunted Armature Control Method
DC series motor by field control may be done by the Field Diverter method. Analyzing the transfer function of a field-controlled DC motor offers seve
and understanding the dynamic response². However, this method is not without its drawbacks. It can cause changes in the motor losses and is not
controlling DC motors, providing better efficiency at higher speeds and more accurate position control

64. A 6-pole lap wound shunt motor has 500 conductors in the armature. The resistance of armature path is 0.05 ohm. The resistance of shunt field is 25 ohm.
0.02 Wb.
Answer: Shunt field current Ish= V/Rsh=100/25=4 A. Armature current Ia=IL-Ish=120-4=116 A. Back emf Eb=V-IaRa=100-116*0.05=94.2 V. Speed of mo

65. A 6-pole lap wound shunt motor has 500 conductors in the armature. The resistance of the armature path is 0.05 ohm. The resistance of the shunt field is 2
per pole is 0.02 Wb.
Answer: Shunt field current Ish= V/Rsh=100/25=4 A. Armature current Ia=IL-Ish=120-4=116 A. Back emf Eb=V-IaRa=100-116*0.05=94.2 V. Speed of mo

66. A 11 kV/400 V distribution transformer takes a no-load primary current of 1 amp at a power factor of 0.24 lagging. Calculate the core loss current, the magn
 Answer: Exciting or no-load current, I0=1A. Primary voltage, V1 = 11kV = 11000 V. Core loss current, Ic=I0cos(Ⴔ)= 1*0.24=0.24A (Ans). Magnetizing cur

67. A 4 pole 220 V dc shunt motor has armature and shunt field resistance of 0.2 ohm and 220 ohm respectively. It takes 20 A at 220 v from the source while ru
Answer: Supply voltage V=220 V. Line current I=20 A. Armature resistance Ra=0.2 ohm. Shunt field resistance Rsh=220 ohm. Speed N=1000 rpm. Sh
Eb=V-IaRa=216.2 V

68. Describe the discussion on the speed control methods of a DC shunt motor.
Answer: The back emf Eb of a DC motor is nothing but the induced emf in armature conductors due to rotation of the armature in the magnetic
PØNZ/60A. (where, P = no. of poles, Ø = flux/pole, N = speed in rpm, Z = no. of armature conductors, A = parallel paths). Eb can also be given as, Eb
constants Therefore, N ∝ K Eb/Ø (where, K=constant). This shows the speed of a DC motor is directly proportional to the back emf and inversely p
speed of a DC motor is inversely proportional to the flux per pole. Thus by decreasing the flux, speed can be increased and vice versa. To control the fl
more resistance in series with the field winding will increase the speed as it decreases the flux. In shunt motors, as the field current is relatively
increased above the rated value by reducing flux with this method, it puts a limit to maximum speed as weakening of field flux beyond a limit wi
directly proportional to the back emf Eb and Eb = V - IaRa. That means, that when the supply voltage V and the armature resistance Ra are kept con
in series with the armature, Ia decreases and, hence, the speed also decreases. Greater the resistance in series with the armature, greater the decre
field is connected to a fixed exciting voltage and armature is supplied with different voltages. Voltage across armature is changed with the help of su
b) Ward-Leonard System: This system is used where very sensitive speed control of the motor is required (e.g. electric excavators, elevators, etc.).

69. A transformer has 200 turns in the primary coil and 800 turns in the secondary coil. If the primary current is 4A, estimate the secondary current (assuming a
Answer: "Turns ratio = Np/Ns = 200/800 = 1/4 Ip/Is = Ns/Np Is = Ip * (Np/Ns) = 4A * (1/4) = 1A "

70. A transformer core has a maximum flux density of 1.2 T. The core cross-sectional area is 50 cm². The primary winding has 500 turns. If the supply frequency
Answer: "The maximum flux: B = Φ/A Φ = B * A = 1.2 T * (50 * 10^-4 m²) = 0.006 Wb The maximum induced EMF Emax = 4.44 * f * N * Φ = 4.44 * 50 H

71. A transformer has 2000 turns on the secondary winding and produces a maximum induced EMF of 311.1 V. The supply frequency is 60 Hz. Calculate the ma
Answer: Rearrange the EMF equation to solve for maximum flux: Φ = Emax / (4.44 * f * N) Φ = 311.1 V / (4.44 * 60 Hz * 2000 turns) = 0.000585 Wb

72. Describe different types of losses occurring in a transformer. Define the process to reduce eddy current loss
Answer: Transformer losses primarily consist of core losses and copper losses. Core losses, further divided into hysteresis and eddy current losses,
caused by the resistance of the windings, vary with the square of the load current. Lamination is the primary method to reduce eddy current loss in
thin sheets or laminations. 2. Insulation: These laminations are insulated from each other using a thin layer of varnish or oxide. 3. Current Path: Whe
(eddy currents). However, the laminations offer high resistance to these currents due to their thin thickness and insulation. 4. Reduced Eddy Curre
the associated power loss. By limiting the path for eddy currents to flow, lamination effectively decreases their magnitude and consequently reduces
silicon steel have higher resistivity than pure iron, reducing eddy current flow. • Lowering operating frequency: As eddy current loss is proportio
However, this is often not practical for most applications.

73. A magnetic circuit having 150 turns coils and the cross-sectional area and length of the magnetic circuit are 5*10^-4 m^2 and 25*10^-2 m respectively. Dete
0.3*10^-3 wb
Answer: "I=2A MMF=NI=150*2=300 AT H=NI/l=300/(25*10^-2)=1200A/m B=(flux(∅))/(area(a))=(0.3*10^-3)/(5*10^-4)=0.6T µ=B/H=0.6/1200=500*10

74. State Ohm's law.

Answer: "Ohm's law states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided th

75. Explain Faradays laws of electromagnetic induction.

Answer: "Faraday's law is a fundamental principle in electromagnetism that describes how a magnetic field can induce an electric current in a co
magnetic flux linked with a coil, an emf is induced in the coil. • This induced emf is called induced electromotive force. • If the circuit is closed, an in
coil is equal to the rate of change of magnetic flux linked with the coil. • Mathematically, this can be expressed as: ε = -N(dΦ/dt) "

76. Explain Fleming left hand rule.

Answer: "Fleming's left-hand rule is a simple way to remember the relationship between the direction of motion, the direction of the magnetic field
hand so that your thumb, index finger, and middle finger are mutually perpendicular (forming an ""L"" shape). Thumb: Points in the direction of t
finger: Points in the direction of the induced current."

77. Describe the significance of the hysteresis loop in a B-H curve. Describe the factors affecting the shape and area of the hysteresis loop.
Answer: "The hysteresis loop in a B-H curve is a graphical representation of the relationship between magnetic flux density (B) and magnetic field
provides valuable insights into the magnetic properties of a material. Significance of the hysteresis loop: • Hysteresis loss: The area of the hysteresis
larger area indicates higher energy loss, which is undesirable in many applications. • Retentivity: The point on the B-axis when H is reduced to ze
magnetizing field is removed. • Coercivity: The point on the H-axis when B is reduced to zero is called coercivity. It represents the magnetizing force
hysteresis loop: • Material composition: Different materials exhibit different hysteresis loops. Ferromagnetic materials with higher permeability tend
the hysteresis loop. • Magnetic history: The previous magnetic state of the material can influence the shape of the loop. • Grain size: Smaller grain si

78. Calculate the current of each loop.

Answer: Let the two loop currents be I1 and I2. Applying KVL in loop 1 (left hand loop) 100 - 5I1 - 6(I1 - I2) = 0 or, 11I1 - 6 I2 = 100 (1) Applying KVL in
get, I1 = 10.4 A and I2 = 2.6 A

79. Calculate the current through 8 ohm resistance using thevenin's theorem.
 Answer: Removing the load resistance and calculating Vth =100- 100/11 x 5 = 54.55 V Removing the voltage and replacing it by a short circuit. Then, R

80. Calculate the branch current using 15 ohm resistance.

Answer: Let I! and I2 be the loop currents (clockwise) Applying KVL to loop 1 (left hand loop) 10 - 10 I1 -25 (I1 - I2) - 5 I1 = 0 or, 8 I1 - 5 I2 = 2 (1) Appl
(1) and (2) we get, I2 = -0.48 A. Thus the actual direction of current will be opposite to that assumed. Thus current through 15 ohm resistor is 0.48 A.

81. Calculate the current for each loop.

Answer: Loop currents are considered as I1, I2, I3 for loop 1, 2, 3, respectively. the corresponding loop equations are formed as, 140(I1)-50(I2)-30(I3
det=601000; det1=991000;det2=1275000; det3=897000. Therefore, I1=det1/det=991000/601000=1.64A. I2=det2/det=1275000/601000=2.12A. I3=d

82.

Calculate the number of node, junction and branches.

Answer: Node: point in a network at which two or more circuit elements are joined, Juntion: point in a network at which three or more circuit eleme
=4, branch= 9

83. State Thevenin's theorem and Norton's theorem.

Answer: The current flowing through a load resistance RL connected across anyb two terminals A and B of a linear, active and bilateral network is give
removal of RL and Ri is the internal resistance of the network as viewed back into the open circuited network from terminals AB deactivating all
bilateral network when viewed from its load terminals is equivalent to a constant current source and an internal (parallel resistance). the constant cu
through the load terminals. The internal resistance is the equivalent resistance of the network looking back into the terminals with all the sources rep

84. An alternating voltage is given by the equation v = 282.4 sin (377t + π/6). Calculate rms value, frequency and the time period.
Answer: Vm = 282.84 V. Thus, Vrms = 0.707x282.84 = 200V. ω = 377 rad/s, f = 377/2π = 60 Hz. T=1/f = 0.0167 s

85. A circuit consists of a capacitor of 300 micro F alone connected across an alternating voltage of v=100 sin 100πt. Estimate the expression for current.
Answer: C = 300 micro F. Thus, XC = 1/ωC = 10.61 ohm. Thus, iC = Vm/Xc sin(100 πt + π/2) = 100/10.61 sin(100 πt + π/2) = 9.425sin(100 πt + π/2)

86. Define node, junction, loop and mesh of a circuit.

Answer: Node is a junction in a circuit where two or more circuit elements are connected together. Junction is a point in a circuit where the div
encountered more than once. Mesh is a loop which does not contain any other loop inside it.
87. A 10 V voltage source with 1 ohm internal resistance is connected with load resistance of 10 ohm. Calculate the values of the Norton equivalent resistance
Answer: step 1: remove load resistance. Step 2: short circuit the removed load resistance terminal and find the short circuit current i.e., 10 A. Step 3: fi
is 1 ohm. Therefore, In=10 A and Rn=1 ohm.

88. A 10 V voltage source with 1 ohm internal resistance is connected with load resistance of 4 ohm. Calculate the values of the Thevenin equivalent resistance
Answer: step 1: remove load resistance. Step 2: Open circuit the removed load resistance terminals and find the open circuit voltage i.e., 10 V. Step
resistance is 1 ohm. Therefore, Vth=10 V and Rth=1 ohm and load current = Vth/(Rth+Rl)=10/(1+4)=2A.

89. Distinguish between intrinsic and extrinsic semiconductors and explain the term "Doping"

Answer:

90. Explain the Drift current and Diffusion current in a semiconductor device.

Answer:
91. Explain intrinsic and extrinsic semiconductors and describe the crystal structure for both the cases.

Answer:
92. A silicon semiconductor is doped with a donor impurity concentration of 5×1015cm−3. Assuming complete ionization, calculate the electron and

Answer:
93.

Answer:

94. Explain the working of NPN transistor.

Answer:

95. Explain the working of PNP transistor.

Answer:

96. Illustrate the Input and Output characteristics of CE configuration.

 Answer:

97. Explain the input output characteristics of CB connection.

Answer:
98. Develop the circuit connection of a transistor in CC configuration and discuss about current amplification factor in CC configuration.

Answer:

99. Comparison between CB, CE and CC configuration of Transistor.

Answer:

100. A transistor is connected in common emitter (CE) configuration in which collector supply is 8 V and the voltage drop across resistance RC connected
voltage (ii) base current.

Answer:
101. In a common base connection, α = 0.95. The voltage drop across 2 kΩ resistance which is connected in the collector is 2V. Find the base current.

Answer:

102.

Calculate current through 12 ohm resistance by superposition theorem.

Answer:
 Replace 60V voltage source with internal resistance of 0.5Ω

RT=((R1+r)×R3/(R1+r)+R3)+R2
RT=((0.5×24)×12/(0.5+24)+12)+10

RT=14.1Ω

I′2=V2/RT=48/14.1

I′2=3.4 A

I′3=I′2×(V+R1/(V+R1)+R3))
I′3=3.4×((0.5+24)/(0.5+24)+12))

I′3=3.4×0.67I3′=3.4×0.67

I′3=2.278A

I′1=I′2−I′3

I′1=3.4−2.278

I′1=1.122 A

Step 2: Replace 48V voltage source with Short circuit

Total resistance as seen by the battery is 0.5+24+(12/110)=29.95Ω

Total current supplied by 60 V = (\frac{60}{29.95}=2\ A\)

I′′2=(2×10)/22=0.91 A

I2=(2×12)/22=1.091 A

Now by applying the superposition theorem

2 - 0.875 = 1.0125 A

I1=1.091−2.66=1.569 (from 48 V side)

I12=I′12+I′′12

I12=0.91+1.785=2.695 A

103. In a bridge-type rectifier circuit, the diodes are assumed to be ideal. Assume primary to secondary turns to be 4. Given, R.M.S. primary voltage
voltage, (ii) PIV, (iii) output frequency.
 Answer:

104. 230 V, 50 Hz AC voltage is applied to a bridge rectifier through a step-down transformer (4:1). Load resistance connected to the rectifier is 1 kilo
power delivered to the load.

Answer:

105. An AC supply of 230 volts is applied to a half-wave rectifier circuit through a transformer with a turn ratio of 10:1. Calculate: (i) output DC voltage, (i

Answer:
106. A crystal diode having internal resistance rf = 20 Ω is used for half-wave rectification. If the applied voltage is v = 50 sinωt and the load resistance
(iv) efficiency of rectification.

Answer:

107. Describe DC and AC resistance and junction resistance of a diode.

Answer:
108. Justify at room temperature (t = 25 oC) that the junction resistance of an diode (rj) is equal to 26/IF, where IF is the forward current, and consider η =

Answer:

109. Justify the DC output power is maximum in a half-wave rectifier when the load resistance is equal to the forward resistance.

Answer:
110. Explain the effects of temperature on diode current.

Answer:

111. Explain the effects of temperature on diode current.

Answer:
112. Compare various types of filter circuits (L, C, LC, and π filter).

Answer:

113. Compare in between BJT and FET.

Answer:
114. Explain the working principle of JFET.

Answer: The working of JFET can be explained as follows:

Case-a:

When a voltage VDS is applied between drain and source terminals and voltage on the gate is zero as sh
layers.

Fig.1a

The electrons will flow from source to drain through a channel between the depletion layers.

The size of the depletion layers determines the width of the channel and hence current conduction through

Case-b:

When a reverse voltage VGS is applied between gate and source terminals, as shown in fig.1(b), the width

Fig.1 b

This reduces the width of conducting channel, thereby increasing the resistance of n-type bar.

Consequently, the current from source to drain is decreased.

On the other hand, when the reverse bias on the gate is decreased, the width of the depletion layer also decr

This increases the width of the conducting channel and hence source to drain current.

A p-channel JFET operates in the same manner as an n-channel JFET except that channel current carriers w

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