Practice questions of BEE
Module-1
Determine the potential difference V AB for the given network.
Determine the equivalent resistance between terminals A and B.
Find an equivalent resistance between terminals A and B.
Determine the equivalent resistance across terminals A and B.
Convert the given circuit into a single current source in parallel with a single resistance
between points A and B using source transformation.
Find the value of current flowing through 5Ω resistor by using Mesh analysis.
Determine the value of current flowing through the 2 Ω resistor using mesh analysis.
Determine the value of current flowing through the 2 Ω resistor using Mesh analysis.
Explain the concept of source transformation along with its advantages.
Calculate the value of current flowing through the 10 Ω resistor using Thevenin’s
theorem.
State Maximum Power Transfer Theorem. Derive equation for maximum power delivered
to load.
Calculate the value of the resistance RL for maximum power transfer and calculate the
maximum power.
Determine the value of current flowing through the 3 Ω resistor using Node analysis.
Find the value of current flowing through 2Ω resistor by using Node Analysis.
Module-2
What do you mean by symmetric and asymmetric waveform? Write a formula to
calculate the average and rms value.
Write a short note on generation of single phase alternating current.
Two sinusoidal currents are given as i1 = 10 √2 sin ωt and i2 = 20 √2 sin (ωt+60°).Find
the expression for the sum of these currents.
Derive the resonant frequency for series resonance in a single phase ac circuit.
Explain the behavior of pure resistor in an ac circuit.
An ac circuit consists of a pure resistance of 10 ohms and is connected across an ac
supply of 230 V, 50 Hz. Calculate (i) current, (ii) power consumed, (iii) power factor, and
(iv) write down the equations for voltage and current.
An alternating voltage is represented by v = 141.4 sin 377t. Calculate (i) max-value, (ii)
frequency, and (iii) time period.
An alternating current is given by i = 14.14 sin 377 t. Find (i) rms value of the current,
(ii) frequency, (iii) instantaneous value of the current when t = 3 ms, and (iv) time taken
by the current to reach 10 A for the first time after passing through zero.
An alternating voltage is represented by v = 141.4 sin 314t. Calculate (i) rms value, (ii)
average value, and (iii) instantaneous value of voltage, when t is 3 ms.
Evaluate average, rms, form factor and peak factor.value of following waveform.
Determine the average and rms values of the waveform shown in figure below.
A resistor of 20ohm, inductor of 0.05 H and a capacitor of 50 mF are connected in series.
A supply voltage 230 V, 50 Hz is connected across the series combination. Calculate the
following: (i) impedance, (ii) current drawn by the circuit, (iii) phase difference and power
factor, and (iv) active and reactive power consumed by the circuit.
A resistor of 20 Ω, inductor of 0.05 H and a capacitor of 50 μF are connected in series. A
supply voltage 230 V, 50 Hz is connected across the series combination. Calculate the
impedance, current drawn by the circuit, power factor, and active power.
Determine the supply current, current in each branch and the total power factor of the
circuit shown below.
A series R-L-C circuit consists of R = 10 Ω, L = 0. 2 H and C = 40 µF. The applied
voltage across the circuit is 100 V ac.
Calculate the resonant frequency, quality factor, current at resonance and the voltage drop
across L or C of the circuit.
A series R-L-C circuit consists of R = 1000 Ω, L = 100 mH and C = 10 µF. The applied
voltage across the circuit is 100 V.
(i) Find the resonance frequency of the circuit.
(ii) Find quality factor of the circuit at resonant frequency.
(iii) Calculate the bandwidth of the circuit.
Module-3
Write a short note on generation of three phase ac.
Explain the basic principle of wattmeter.
Explain with neat diagram Three-Wattmeter method to measure power in three phase ac
with its advantages and disadvantages?
Two wattmeters are used to measure power in a 3-ϕ balanced star connected load using
the two-wattmeter method. The readings of the 2 wattmeters are 8 kW and 4 kW
respectively. Calculate the total power consumed by the 3-ϕ load and the power factor.
Three coils, each having a resistance of 8 Ω and an inductance of 0.02 H, are connected
in delta to a three-phase, 400 V, 50 Hz supply. Calculate the (i) line current, and (ii)
power absorbed.
Three equal impedances, each of 8 + j10 ohms, are connected in star. This is further
connected to a 440 V, 50 Hz, three-phase supply. Calculate (i) phase voltage, (ii) phase
angle, (iii) phase current, (iv) line current.
Derive the relationship of line voltage, line current, phase voltage and phase current in
balanced star and delta connected load of three phase ac.
Three similar coils each having a resistance of 10 Ω and inductance of 0.04 H are
connected in star across a 3 phase, 50 Hz, 200 V supply. Calculate the line current, total
power absorbed, reactive volt amperes and total volt amperes.
Module-4
With the help of a neat diagram, explain the working principle of a single phase
transformer.
A 3000/200 V, 50 Hz, single-phase transformer has a cross-sectional area of 150 cm2 for
the core. If the number of turns on the low-voltage winding is 80, determine the number
of turns on the high-voltage winding and maximum value of flux density in the core.
An 80 kVA, 3200/400 V, 50 Hz single-phase transformer has 111 turns on the secondary
winding. Calculate (i) number of turns on primary winding, (ii) secondary current, and
(iii) cross-sectional area of the core, if the maximum flux density is 1.2 teslas.
Compare core type and shell type single phase transformers.
Explain different types of losses for single phase transformer.
A 5 kVA, 1000 V/200 V, 50 Hz, 1-ϕ transformer gave the following test results:
OC test (HV side) 1000 V, 0.24 A, 90 W
SC test (HV side) 50 V, 5 A, 110 W
Calculate the equivalent circuit parameters referred to HV side and also in LV side.
Derive the emf equation of a single phase transformer.
Module-5
Derive emf equation of a DC generator.
Explain the principle of operation of a DC motor.
A six-pole lap-wound armature has 840 conductors and a flux per pole of 0.018 Wb.
Calculate the emf generated, when the machine is running at 600 rpm.
With the help of a neat diagram, explain the operating principle of a three phase induction
motor.
Compare squirrel cage induction motor and slip ring induction motor.
Explain in brief 3 phase squirrel cage induction motor.
With neat diagram explain the main parts of dc machine. Mention the functions of each
part.
Module-6
Explain the necessity of earthing. Illustrate different types of earthing with suitable
diagram.
Explain various types of wires and cables used in electrical installation.
Write short notes on LT switch gear
