Alternating Current

Which one of the following graphs gives the variation of

Mean Value and Virtual voltage with time? (1994)
Value of A.C. 1|
b

1. A standard filament lamp consumes 100 W when connected

to 200 V ac mains supply. The peak current through the bulb
will be:
(2022 Re)
d
a. 2 A b. 0.707 A
c. 1A d. 1.414

2. The peak voltage of the ac source is equal to (2022)

times the rms value of the source
a.
A.C. Circuit Containing
b. the value of voltage supplied to the circuit Capacitance Only
c. the rms value of the ac source
d. V2 times the rms value of the ac source
6. Given below are two statements. (2022 Re)
3. The r.m.s. value of potential difference V shown in the figure
Statement I: In an ac circuit, the current through a capacitor
is: (2011 Mains) leads the voltage across it.
Statement Il: In a.c. circuits containing pure capacitance
only, the phase difference between the current and the voltage
is n.

In the light of the above statements, choose the most

T/2 T
appropriate answer from the options given below
a. Vo b. V. / V2 a. Statement I is incorrect but Statement Il is correct
b. Both Statement and Statement Il are correct
c. V/2
c. Both Statement I and Statement II are incorrect
4. In an A.C. circuit, Ims and I, are related as [MR*] (1994)
d. Statement I is correct but Statement Il is incorrect
a. Arms b. I ms = V21o 7. A capacitor of capacitance 'C', is connected across an ac
d. Arms = 1, /V2 source of voltage V, given by V = V, sin wt. The displacement
current between the plates of the capacitor, would then be
given by: (2021)
Self Inductance
Vo cos ot
a. 1, = b. 1a = - sin ot
5. The current I in an A.C. circuit inductance coil varies with
00 00

time according to the graph given below.

8. A 40 uF capacitor is connected to a 200V, 50Hz ac supply.

The rms value of the current in the circuit is, nearly: (2020)
a. 2.05 A b. 2.5 A

c. 25.1 A d. 1.7 A
 Chapter & Topicwise NEET PYQ's

9. A small signal voltage Vt) = Vsinat is applied across an

15. A resistance R draws power P when connected to an AC
ideal capacitor C : (2016 - 1)
source. If an inductance is now placed in series with the
resistance. such that the impedance of the circuit becomes Z.
be: (MR*](2015)
a. Current I(t) lags voltage V(t) by 90° the power drawn will
b. Over a full cycle the capacitor C does not consume any b. P
R

energy from the voltage source a.P

c. Current I(t) is in phase with voltage V(t) R
d. P
d. Current I(t) leads voltage V(t) by 180° c. P

10. In an AC circuit an alternating voltage E = 200/2 sin 100t

volts is connected to a capacitor of capacity 1 uF. The r.m.s 16. A coil of self-inductance L is connected in series with a bulb
value of the current in the circuit is:
B and an AC source. Brightness of the bulb decreases when:
[MR*] (2011 Pre)
(2013)
a. 10 mA b. 100 mA the coil
a. An iron rod is inserted in
c. 200 mA d. 20 mA
b. Frequency of the AC
source is decreased
11. A capacitor of capacity C and reactance X if capacitance and c. Number of turns in the coil is reduced
frequency become double then reactance will be: (2001) d. A capacitance of reactance X, = X, is included in the same
circult
a. 4X b.
2 17. A coil has resistance 30 ohm and inductive reactance
20 ohm at 50 Hz frequency. If an AC source, of
d. 2X 200 volt, 100 Hz, is connected across the coil, the current in
the coil will be: (2011 Mains)
a. 4.0 A b. 8.0 A

20 d. 2.0 A
A.C. Circuit Containing C.
/13
A

R and L Only 18. An AC voltage is applied to a resistance R and an inductor L

in series. If R and the inductive reactance are both equal to
3 S2, the phase difference between the applied voltage and the
12. An ac source is connected in the given circuit. The value of current in the circuit is:
(2011 Pre)
will be:
(2023-Manipur) а. п/6 b. n/4
100
С. п/2 d. Zero
000000

A.C. Circuit Containing

R and C Only
V = 220 sin (100mt +ф) volt
19. A series RC circuit is connected to an alternating
a. 60° b. 90° voltage
source. Consider two situations
C. 30° d. 45°
A. When capacitor is air filled
13. An inductor of inductance 2 mH is connected to a 220 V, 50 B. When capacitor is mica filled
Hz a.c. source. Let the inductive reactance in the circuit is X,. Current through resistor is i and voltage across capacitor is V
then:
If a 220 V dc source replaces the ac source in the circuit, then (2015 Re)
the inductive reactance in the circuit is X, [MR*] (2022 Re) a. V = V

X, and X, respectively are c. V. > Vo d. I, > 4

a. 0.628 w, infinity b. 6.28 w, zero 20. When the key K is pressed at time t = 0, then which of the
c. 6.28 w, infinity d. 0.628 w, zero following statement about the current I in the resistor AB of
the given circuit is true?
14. A light bulb and an inductor coil are connected to an ac source (1995)
2V
through a key as shown in the figure below. The key is closed
and after sometime an iron rod is inserted into the interior of
10009 U
the inductor. The glow of the light bulb (2020-Covid)
000000
1 uF 0001
a. I Oscillates between 1 mA
and 2 mA
b. at t = 0, I = 2 mA and with time
it goes to 1 mA
a. Remains unchanged b. Will fluctuate c. I = 1 mA at all t
c. Increases d. Decreases
d. I = 2 mA at all t
 Alternating Current

21. The time constant of C-R circuit is (1992) 26. An inductor of inductance L, a capacitor of capacitance C
series to an
a. 1/CR b. C/R and a resistor of resistance 'R' are connected in
shown in figure.
c. CR d. R/C ac source of potential difference 'V' volts as
Potential difference across L, C and R is 40V, IOV and 40V,
LCR
respectively. The amplitude of current flowing through
A.C. Circuit Containing series circuit is 10/2 A. The impedance of the circuit is:
[MR *] (2021)
R, L and C

<40V→< 10V→ < 40V→

22. In aseries LCR circuit, the inductance L is 10 mH, capacitance
C is IF and resistance R is 1002. The frequency at which
resonance (2023) a. 5/ 522 b. 49
a. 1.59 kHz c. 5.02 d. 4/25
b. 15.9 rad/s resistors
27. Figure shows a circuit that contains three identical
c. 15.9 kHz with resistance R = 9.0 § each, two identical inductors with
d. 1.59 rad/s inductance L = 2.0 mH each, and an ideal battery with emf
£ = 18 V. The current 'i' through the battery just after the
23. The net impedance of circuit (as shown in figure) will (2017-Delhi)
switch closed is:
be: (2023)

- mH 10°- UF
1092 el er
R
R R

a. 0.2 A b. 2 A
220V, 50Hz c. 0 ampere d. 2 mA
with an
a. 25 W b. 10V2 52 28. In a circuit L, C and R are connected in series
d. SV552 alternating voltage source of frequency f. The current leads
c.15W the voltage by 45º. The value of C is: (2005)
24. If Z, and Z, are the impedances of the given circuits (a) b.
and (b) as shown in figures, then choose the correct option
(2023-Manipur)
d.
00000 -w
109 109
5 mH 10*
- HF

Electric Resonance

K 220 V, 50 Hz
6V 29. A series LCR circuit with inductance 10 H, capacitance
(a) 10 uF, resistance 50 2 is corrected to an ac source of voltage,
V = 200 sin(100t) volt. If resonant frequency of the LCR
a. 2, <Z, b. Z, +Z, = 20 w
circuit is v, and the frequency of the ac source is v, then:
c. Z, = 2, d. Z, > Z2 (2022)
25. For every high frequencies, the effective impedance of the 100

circuit (shown in the figure) will be: (2023-Manipur) a. v = 100Hz; Vo b. v, = v = 50 Hz

1 uF 1 mH 50 50
19
000000 c. Vo = V = d. Vo - Hz, v = 50 Hz

2 uF 30. A series LCR circuit is connected to an ac voltage source.

When L is removed from the circuit, the phase difference
0000000
2 mH 392 29 between current and voltage is . If instead C is removed
3

from the circuit, the phase difference is again between

3

a. 4 W b. 6 W current and voltage. The power factor of the circuit is:

c. 1 W d. 3 W (2020)
 Chapter & Topicwise NEET PYQ's
а. 0.5
b. 1.0
с. -1.0
d. Zero Energy Stored in Condenser,
31. Which of the following combinations should be selected for Inductor and LC Oscillations
better tuning of an L-C-R circuit used for communication?
(2016 - I1) 37. The magnetic energy stored in an inductor of inductance
a. R = 15 2, L = 3.5 H, C = 30 uF 4 uH carrying a current of 2 A is: (2023)
b. R = 25 S2, L = 1.5 H, C = 45 uF a. 8 MJ b. 4 MJ
c. 4 mJ d. 8 mJ
c. R = 20 S, L = 1.5 H, C = 35 uF
d. R = 25 2, L = 2.5 H, C = 45 uF 38. A condenser of capacity C is charged to a potential difference
of V,. The plates of the condenser are then connected to
32. In an electrical circuit R, L, C and an AC voltage source are
an ideal inductor of inductance L. The current through the
all connected in series. When L is removed from the circuit, inductor when the potential difference across the condenser
the phase difference between the voltage the current in the reduces to V, is: [MR*] (2010 Mains)
circuit is n/3. If instead, C is removed from the circuit, the
phase difference is again /3. The power factor of the circuit a.
1S:
[MR*] (2012 Pre)
a. 1/2 b.

d.
c. 1 d. 3/2
33. In the given circuit the reading of voltmeter V, and V, are 39. A transistor-oscillator using resonant circuit with an
300 volts each. The reading of the voltmeter V, and ammeter A inductor L (of negligible resistance) and a capacitor C in
are respectively: (2010 Pre) series produce oscillations of frequency f. If L is doubled and
R = 100 2
C is changed to 4C, the frequency will be: (2006)
a. f/4 b. 8f
d. 2f

Average Power and Power

220 V, 50 Hz
Associated with A.C. Circuits and
a. 100 V, 2.0 A b. 150 V, 2.2 A
Power Factor
c. 220 V, 2.2 A d. 220 V, 2.0 A
34. What is the value of inductance L for which the current
is maximum in a series LCR circuit with C = 10
uF and
40. The maximum power is dissipated for an ac in a/an:
• = 1000 s': (2023-Manipur)
(2007) a. resistive circuit
a. 1 mH
b. LC circuit
c. inductive circuit
d. capacitive circuit
b. Cannot be calculated unless R is known
41. A series LCR circuit containing 5.0 H inductor, 80 uF
c. 10 mH capacitor and 40 S2 resistor is connected to 230 V variable
d. 100 mH frequency ac source. The angular frequencies of the source at
which power transferred to the circuit is half the power at the
35. The value of quality factor is: (2000) resonant angular frequency are likely to be: [MR*] (2021)
oL a. 50 rad/s and 25 rad/s
a. b.
R b. 46 rad/s and 54 rad/s
c. 42 rad/s and 58 rad/s
d. L/R
d. 25 rad/s and 75 rad/s
36. An series L-C-R circuit is connected to a source of A.C.
current. At resonance, the phase difference between the applied 42. An inductor 20mH, a capacitor 100 uF and a resistor 50 g
voltage and the current in the circuit, is [MR*] (1994) are connected in series across a source of emf, V = 10 sin
314 t. The power loss in the circuit is (2018)
b. Zero
a. 2.74 W
b. 0.43 W
с. п/4 d. n/2 c. 0.79 W
d. 1.13 W
 Alternating Current

43. The potential differences across the resistance, capacitance 50. In an ac, circuit with phase voltage V and current I,
and inductance are 80 V, 40 V and 100 V respectively in an the power dissipated is
(1997)
LCR circuit. The power factor of this circuit is: (2016 - ID)
a. V.I
2. 0.8 b. 1.0
d. 0.5 b. Depends on phase angle between V and I
c. 0.4
1. An inductor 20 mH, a capacitor 50 uF and a resistor 40 2 are C.
connected in series across a source of emf V = 10 sin 340t.
The power loss in A.C. circuit is: (2016 - 1) d.
a.0.51W b. 0.67 W

c.0.76W
d. 0.89 W 51. In an A.C. circuit, the current flowing is 1 = 5 sin (100t - n/2)
(100t) volts.
ampere and the potential difference is V = 200 sin
45. The instantaneous values
as
of alternating current and voltages The power consumption is equal to (1995)
in a circuit are given
a. 20 W b. 0 W
1=• -sin(100rt) ampere
c. 1000 W d. 40 W

52. Two cables of copper are of equal lengths. One of them has
- sin 1001 + 3 a single wire of area of cross-section A, while other has
10 wires of cross-sectional area A/10 each. Give their,
The average power in watts consumed in the circuit is:
suitability for transporting A.C. and D.C (1994)
(2012 Mains)
b.
a. Only multiple strands for A.C., either for D.C.
a. 1/4 b. Only multiple strands for A.C., only single strand for D.C.
c. 1/2 d. 1/8 c. Only single strand for D.C., either for A.C.
d. Only single strand for A.C., either for D.C.
46. Power dissipated in an LCR series circuit connected to an AC
source of emfs is: [MR *] (2009)
Transformer
LO Lo-
Co b.
Co
a.
R
53. A 12 V, 60 W lamp is connected to the secondary of a step
R
down transformer, whose primary is connected to ac mains
d. of 220 V. Assuming the transformer to be ideal, what is the
current in the primary winding? (2023)
R' + LO- LO- a. 0.37 A b. 0.27 A
Co Co
c. 2.7 A d. 3.7 A
47. In an AC circuit the e.m.f (e) and the current (i) at any instant
54. A step down transformer connected to an ac mains supply of
are given respectively by
220 V is made to operate at 11 V, 44 W lamp. Ignoring power
e = E sinot losses in the transformer, what is the current in the primary
i= I sin(ot - q) circuit? (2021)
The average power in the circuit over one cycle of a.c. is:
a. 0.4 A b. 2 A
(2008)
c. 4 A d. 0.2 A
b.
a. E,lo
55. A transformer having efficiency of 90% is working on 200 V
E, lo and 3 kW power supply. If the current in the secondary coil is
d.
C.
- sin 6 A, the voltage across the secondary coil and the current in
the primary coil respectively are: (2014)
48. A coil of inductive reactance 31 S2 has a resistance of 8 S2. It is
placed in series with a condenser of 25 S2. The combination is a. 300 V, 15 A b. 450 V, 15 A
connected to an AC source of 110 V. The power factor of the
c. 450 V, 13.5 A d. 600 V, 15 A
circuit is: (2006) 56. A 220 volt input is supplied to a transformer. The output circuit
a. 0.40 b. 0.128 draws a current of 2.0 ampere at 440 volts. If the efficiency
of the transformer is 80%, the current drawn by the
c. 0.80 d. 0.66 primary
windings of the transformer is: [MR *] (2010 Pre)
49. For a series LCR circuit the power loss at resonance is:
a. 5.0 ampere b. 3.6 ampere
(2002)
c. 2.8 ampere d. 2.5 ampere
b. FLo
57. A transformer is used to light a 100 W and 110 V lamp from a
oL
220 V mains. If the main current is 0.5 amp, the
efficiency of
the transformer is approximately: (2007)
c. FR d. a. 50% b. 90%
Co
c. 10% d. 30%
82
Chapter & Topicwise NEET PYQ's

58. The primary and secondary coil of a transformer have 50 and 60. Turn ratio of a step-up transformer is 1: 25. If current in load
1500 turns respectively. If the magnetic flux @ linked with the coil is 2 A, then the current in primary coil will be: (1998)
primary coil is given by ф = d. + 41, where is in Webers, t is
time in seconds and , is a constant, the output voltage across a. 25 A b. 50 A
the secondary coil is: (2007) d. 0.5 A
c. 0.25 A
a. 120 volts b. 220 volts
c. 30 volts d. 90 volts 61. The primary winding of a transformer has 500 turns whereas
59. The core of a transformer is laminated because: (2006) its secondary has 5000 turns. The primary is connected to an
a. Energy losses due to Eddy currents may be minimised A.C. supply 20 V, 50 Hz. The secondary will have an output
b. The weight of the transformer may be reduced of
(1997)
c. Rusting of the core may be prevented
a. 2 V, 50 Hz b. 2 V, 5 Hz
d. Ratio of voltage in primary and secondary may be
increased c. 200 V, 50 Hz d. 200 V, 500 Hz

Answer Key

1. (b) 2. (d) 3. (b) 4. (d) 5. (a) 6. (d) 7. (d) 8. 9. (b) 10. (d)
11. (c) 12. (d) 13. (d) 14. (d) 15. (d) 16. (a) 17. (a) 18. (b) 19. (c) 20. (b)
21. 22. (a) 23. (d) 24. (a) 25. 26. 27. (none) 28. (a) 29. (c) 30. (b)
31.(a) 32. (c) 33. (c) 34. (d) 35. (a) 36. 37. (a) 38. (d) 39. (c) 40. (a)
41. (b) 42. (c) 43. (a) 44. (a) 45. (d) 46. (d) 47. (d) 48. (c) 49. (c) 50. (b)
51. (b) 52. (a) 53. (b) 54. (d) 55. (b) 56. (a) 57. (b) 58. (a) 59. (a) 60. (b)
61. (c)