Alternating Current: JEE Advanced - Physics, Solution by DC Pandey NEET Notes | EduRev

 Page 1


 
For JEE Advanced 
  Objective Questions 
  Single Correct Option 
Q 1.  A capacitor and resistor are connected with an AC source as shown in figure. Reactance of 
capacitor is X
C
 = 3? and resistance of resistor is 4 ?. Phase difference between current I and I
1
 is 
1o
3
tan 37
4
?
?? ??
?
?? ??
?? ??
 
 
  (a) 90°   (b) zero  (c) 53°   (d) 37° 
Q 2.  A circuit contains resistance R and an inductance L in series. An alternating voltage V = V
0
 sin ?t
 
is applied across it. The currents in R and L respectively will be 
 
 (a) I
R
 = I
0
 cos ?t, I
L
 = I
0
 cos ?t  (b) I
R
 = – I
0
 cos ?t, I
L
 = I
0
 cos ?t 
  (c) I
R
 = I
0
 sin ?t, I
L
 = - I
0
 cos ?t  (d) None of the above 
Q 3.  In the circuit shown in figure, the AC source gives a voltage V = 20 cos (2000t). Neglecting 
source resistance, the voltmeter and ammeter readings will be 
 
  (a) 0 V, 2.0 A   (b) 0 V, 1.4 A  (c) 5.6 V, 1.4 A  (d) 8 V, 2.0 A 
Q 4.  A signal generator supplies a sine wave of 200 V, 5 kHz to the circuit shown in the figure. Then 
choose the wrong statement 
 
  (a) The current in the resistive branch is 0.2 A 
  (b) The current in the capacitive branch is 0.126 A 
  (c) Total line current is ? 0.283 A 
  (d) Current in both the branches is same 
Q 5.  A complex current wave is given by i = (5 + 5 sin 100 ?t)A. Its average value over one time period 
is given as 
  (a) 10 A   (b) 5 A   (c) 50 A
   
(d) 0 
Page 2


 
For JEE Advanced 
  Objective Questions 
  Single Correct Option 
Q 1.  A capacitor and resistor are connected with an AC source as shown in figure. Reactance of 
capacitor is X
C
 = 3? and resistance of resistor is 4 ?. Phase difference between current I and I
1
 is 
1o
3
tan 37
4
?
?? ??
?
?? ??
?? ??
 
 
  (a) 90°   (b) zero  (c) 53°   (d) 37° 
Q 2.  A circuit contains resistance R and an inductance L in series. An alternating voltage V = V
0
 sin ?t
 
is applied across it. The currents in R and L respectively will be 
 
 (a) I
R
 = I
0
 cos ?t, I
L
 = I
0
 cos ?t  (b) I
R
 = – I
0
 cos ?t, I
L
 = I
0
 cos ?t 
  (c) I
R
 = I
0
 sin ?t, I
L
 = - I
0
 cos ?t  (d) None of the above 
Q 3.  In the circuit shown in figure, the AC source gives a voltage V = 20 cos (2000t). Neglecting 
source resistance, the voltmeter and ammeter readings will be 
 
  (a) 0 V, 2.0 A   (b) 0 V, 1.4 A  (c) 5.6 V, 1.4 A  (d) 8 V, 2.0 A 
Q 4.  A signal generator supplies a sine wave of 200 V, 5 kHz to the circuit shown in the figure. Then 
choose the wrong statement 
 
  (a) The current in the resistive branch is 0.2 A 
  (b) The current in the capacitive branch is 0.126 A 
  (c) Total line current is ? 0.283 A 
  (d) Current in both the branches is same 
Q 5.  A complex current wave is given by i = (5 + 5 sin 100 ?t)A. Its average value over one time period 
is given as 
  (a) 10 A   (b) 5 A   (c) 50 A
   
(d) 0 
Q 6.  An AC voltage V = V
o
 sin 100t is applied to the circuit, the phase difference between
 
current and 
voltage is found to be ?/4, then 
 
 (a) R = 100 ?; C = 1 ?F   (b) R = 1k ?; C = 10 ?F  
  (c) R = 10k ?; L = 1H    (d) R = 1k ?; L = 10H 
Q 7.  In series L-C-R circuit voltage drop across resistance is 8 V, across inductor is 6 V and across 
capacitor is 12 V. Then 
  (a) Voltage of the source will be leading in the circuit 
  (b) Voltage drop across each element will be less than the applied voltage 
  (c) Power factor of the circuit will be 3/4 
  (d) None of the above 
Q 8.  Consider an L-C-R circuit as shown in figure, with an AC source of peak value V
o
 and angular
 
frequency ?. Then the peak value of current through the AC source is 
 
 (a) 
0
2
2
V
11
L
RC
??
? ? ?
??
?
??
    (b) 
2
0 2
11
VC
RL
?? ??
? ? ?
?? ??
?
?? ??
 
  (c) 
0
2
2
V
1
RL
C
??
? ? ?
??
?
??
    (d) None of these  
Q 9.  The adjoining figure shows an AC circuit with resistance R, inductance L and source voltage V
s
. 
Then 
 
  (a) the source voltage V
s
 = 72.8 V 
  (b) the phase angle between current and source voltage is tan
-1
(7/2) 
  (c) Both (a) and (b) are correct 
  (d) Both (a) and (b) are wrong 
Q 10.  When an alternating voltage of 220 V is applied across a device P, a current of 0.25 A flows 
through the circuit and it leads the applied voltage by an angle ?/2 radian. When the same voltage 
Page 3


 
For JEE Advanced 
  Objective Questions 
  Single Correct Option 
Q 1.  A capacitor and resistor are connected with an AC source as shown in figure. Reactance of 
capacitor is X
C
 = 3? and resistance of resistor is 4 ?. Phase difference between current I and I
1
 is 
1o
3
tan 37
4
?
?? ??
?
?? ??
?? ??
 
 
  (a) 90°   (b) zero  (c) 53°   (d) 37° 
Q 2.  A circuit contains resistance R and an inductance L in series. An alternating voltage V = V
0
 sin ?t
 
is applied across it. The currents in R and L respectively will be 
 
 (a) I
R
 = I
0
 cos ?t, I
L
 = I
0
 cos ?t  (b) I
R
 = – I
0
 cos ?t, I
L
 = I
0
 cos ?t 
  (c) I
R
 = I
0
 sin ?t, I
L
 = - I
0
 cos ?t  (d) None of the above 
Q 3.  In the circuit shown in figure, the AC source gives a voltage V = 20 cos (2000t). Neglecting 
source resistance, the voltmeter and ammeter readings will be 
 
  (a) 0 V, 2.0 A   (b) 0 V, 1.4 A  (c) 5.6 V, 1.4 A  (d) 8 V, 2.0 A 
Q 4.  A signal generator supplies a sine wave of 200 V, 5 kHz to the circuit shown in the figure. Then 
choose the wrong statement 
 
  (a) The current in the resistive branch is 0.2 A 
  (b) The current in the capacitive branch is 0.126 A 
  (c) Total line current is ? 0.283 A 
  (d) Current in both the branches is same 
Q 5.  A complex current wave is given by i = (5 + 5 sin 100 ?t)A. Its average value over one time period 
is given as 
  (a) 10 A   (b) 5 A   (c) 50 A
   
(d) 0 
Q 6.  An AC voltage V = V
o
 sin 100t is applied to the circuit, the phase difference between
 
current and 
voltage is found to be ?/4, then 
 
 (a) R = 100 ?; C = 1 ?F   (b) R = 1k ?; C = 10 ?F  
  (c) R = 10k ?; L = 1H    (d) R = 1k ?; L = 10H 
Q 7.  In series L-C-R circuit voltage drop across resistance is 8 V, across inductor is 6 V and across 
capacitor is 12 V. Then 
  (a) Voltage of the source will be leading in the circuit 
  (b) Voltage drop across each element will be less than the applied voltage 
  (c) Power factor of the circuit will be 3/4 
  (d) None of the above 
Q 8.  Consider an L-C-R circuit as shown in figure, with an AC source of peak value V
o
 and angular
 
frequency ?. Then the peak value of current through the AC source is 
 
 (a) 
0
2
2
V
11
L
RC
??
? ? ?
??
?
??
    (b) 
2
0 2
11
VC
RL
?? ??
? ? ?
?? ??
?
?? ??
 
  (c) 
0
2
2
V
1
RL
C
??
? ? ?
??
?
??
    (d) None of these  
Q 9.  The adjoining figure shows an AC circuit with resistance R, inductance L and source voltage V
s
. 
Then 
 
  (a) the source voltage V
s
 = 72.8 V 
  (b) the phase angle between current and source voltage is tan
-1
(7/2) 
  (c) Both (a) and (b) are correct 
  (d) Both (a) and (b) are wrong 
Q 10.  When an alternating voltage of 220 V is applied across a device P, a current of 0.25 A flows 
through the circuit and it leads the applied voltage by an angle ?/2 radian. When the same voltage 
source is connected across another device Q, the same current is observed in the circuit but in 
phase with the applied voltage. What is the current when the same source is connected across a 
series combination of P and Q ? 
  (a) 
1
42 
A lagging in phase by ?/4
 
with voltage 
  (b) 
1
42 
A leading in phase by ?/4
 
with voltage 
  (c) 
1
2 
A leading in phase by ?/4 with voltage 
  (d) 
1
42 
A leading in phase by ?/2
 
with voltage 
Q 11.  In a parallel L-C-R circuit as shown in figure if I
R
 , I
L
, I
C
 and I represents the rms values of current 
flowing through resistor, inductor, capacitor and the source, then choose the appropriate correct 
answer 
 
  (a) I = I
R
+I
L
+I
C     
(b) I = I
R
+I
L 
-I
C
 
  (c) I
L
 or I
C
 may be greater than I  (d) None of the above 
Q 12.  In the AC network shown in figure, the rms current flowing through the inductor and capacitor are 
0.6 A and 0.8 A respectively. Then the current coming out of the source is 
 
  (a) 1.0A  (b) 1.4 A  (c) 0.2 A   (d) None of the above 
Q 13.  The figure represents the voltage applied across a pure inductor. The diagram which correctly 
represents the variation of current i with time t is given by 
 
  (a) (b)  (c)  (d)
y
 
Page 4


 
For JEE Advanced 
  Objective Questions 
  Single Correct Option 
Q 1.  A capacitor and resistor are connected with an AC source as shown in figure. Reactance of 
capacitor is X
C
 = 3? and resistance of resistor is 4 ?. Phase difference between current I and I
1
 is 
1o
3
tan 37
4
?
?? ??
?
?? ??
?? ??
 
 
  (a) 90°   (b) zero  (c) 53°   (d) 37° 
Q 2.  A circuit contains resistance R and an inductance L in series. An alternating voltage V = V
0
 sin ?t
 
is applied across it. The currents in R and L respectively will be 
 
 (a) I
R
 = I
0
 cos ?t, I
L
 = I
0
 cos ?t  (b) I
R
 = – I
0
 cos ?t, I
L
 = I
0
 cos ?t 
  (c) I
R
 = I
0
 sin ?t, I
L
 = - I
0
 cos ?t  (d) None of the above 
Q 3.  In the circuit shown in figure, the AC source gives a voltage V = 20 cos (2000t). Neglecting 
source resistance, the voltmeter and ammeter readings will be 
 
  (a) 0 V, 2.0 A   (b) 0 V, 1.4 A  (c) 5.6 V, 1.4 A  (d) 8 V, 2.0 A 
Q 4.  A signal generator supplies a sine wave of 200 V, 5 kHz to the circuit shown in the figure. Then 
choose the wrong statement 
 
  (a) The current in the resistive branch is 0.2 A 
  (b) The current in the capacitive branch is 0.126 A 
  (c) Total line current is ? 0.283 A 
  (d) Current in both the branches is same 
Q 5.  A complex current wave is given by i = (5 + 5 sin 100 ?t)A. Its average value over one time period 
is given as 
  (a) 10 A   (b) 5 A   (c) 50 A
   
(d) 0 
Q 6.  An AC voltage V = V
o
 sin 100t is applied to the circuit, the phase difference between
 
current and 
voltage is found to be ?/4, then 
 
 (a) R = 100 ?; C = 1 ?F   (b) R = 1k ?; C = 10 ?F  
  (c) R = 10k ?; L = 1H    (d) R = 1k ?; L = 10H 
Q 7.  In series L-C-R circuit voltage drop across resistance is 8 V, across inductor is 6 V and across 
capacitor is 12 V. Then 
  (a) Voltage of the source will be leading in the circuit 
  (b) Voltage drop across each element will be less than the applied voltage 
  (c) Power factor of the circuit will be 3/4 
  (d) None of the above 
Q 8.  Consider an L-C-R circuit as shown in figure, with an AC source of peak value V
o
 and angular
 
frequency ?. Then the peak value of current through the AC source is 
 
 (a) 
0
2
2
V
11
L
RC
??
? ? ?
??
?
??
    (b) 
2
0 2
11
VC
RL
?? ??
? ? ?
?? ??
?
?? ??
 
  (c) 
0
2
2
V
1
RL
C
??
? ? ?
??
?
??
    (d) None of these  
Q 9.  The adjoining figure shows an AC circuit with resistance R, inductance L and source voltage V
s
. 
Then 
 
  (a) the source voltage V
s
 = 72.8 V 
  (b) the phase angle between current and source voltage is tan
-1
(7/2) 
  (c) Both (a) and (b) are correct 
  (d) Both (a) and (b) are wrong 
Q 10.  When an alternating voltage of 220 V is applied across a device P, a current of 0.25 A flows 
through the circuit and it leads the applied voltage by an angle ?/2 radian. When the same voltage 
source is connected across another device Q, the same current is observed in the circuit but in 
phase with the applied voltage. What is the current when the same source is connected across a 
series combination of P and Q ? 
  (a) 
1
42 
A lagging in phase by ?/4
 
with voltage 
  (b) 
1
42 
A leading in phase by ?/4
 
with voltage 
  (c) 
1
2 
A leading in phase by ?/4 with voltage 
  (d) 
1
42 
A leading in phase by ?/2
 
with voltage 
Q 11.  In a parallel L-C-R circuit as shown in figure if I
R
 , I
L
, I
C
 and I represents the rms values of current 
flowing through resistor, inductor, capacitor and the source, then choose the appropriate correct 
answer 
 
  (a) I = I
R
+I
L
+I
C     
(b) I = I
R
+I
L 
-I
C
 
  (c) I
L
 or I
C
 may be greater than I  (d) None of the above 
Q 12.  In the AC network shown in figure, the rms current flowing through the inductor and capacitor are 
0.6 A and 0.8 A respectively. Then the current coming out of the source is 
 
  (a) 1.0A  (b) 1.4 A  (c) 0.2 A   (d) None of the above 
Q 13.  The figure represents the voltage applied across a pure inductor. The diagram which correctly 
represents the variation of current i with time t is given by 
 
  (a) (b)  (c)  (d)
y
 
Q 14.  In a series L-C-R circuit, current in the circuit is 11 A when the applied voltage is 220 V. Voltage 
across the capacitor is 200 V. If value of resistor is 20 ?,
 
then the voltage across the unknown 
inductor is 
  (a) zero   (b) 200V   (c) 20 V   (d) None of these 
Q 15.  A steady current of magnitude I and an AC current of peak value I are allowed to pass through 
identical resistors for the same time. The ratio of heat produced in the two resistors will be 
  (a) 2 : 1   (b) 1 : 2   (c) 1:1    (d) None of these 
Q 16.  In the circuit shown in figure, the power consumed is 
 
  (a) zero   (b) 
2
0
V
2R   
(c) 
2
0
2 2 2
VR
2(R L ) ??
  
(d) None of these 
Q 17.  In a series LC circuit, the applied voltage is V
o
. If ? is very low, then the voltage drop
 
across the 
inductor V
L
 and capacitor V
C
 are 
 
 (a) 
00
LC
VV
V ;V
22
??  (b) V
L
 = 0; V
C
 = V
0
 (c) V
L
 = V
0
; V
C
 = 0 (d) V
L
 = -V
C
 = 
0
V
2
 
Q 18.  A coil, a capacitor and an AC source of rms voltage 24 V are connected in series. By varying the 
frequency of the source, a maximum rms current of 6 A is observed. If coil is connected to a dc 
battery of emf 12 volt and internal resistance 4?, then current through it in steady state is 
  (a) 2.4 A   (b) 1.8 A  (c) 1.5 A   (d) 1.2 A 
Q 19.  In a series CR circuit shown in figure, the applied voltage is 10 V and the voltage across capacitor 
is found to be 8 V. The voltage across R, and the phase difference
 
between current and the applied 
voltage will respectively be 
 
 (a) 
1
4
6V, tan
3
?
??
??
??
  (b) 
1
3
3V, tan
4
?
??
??
??
  (c) 
1
3
6V, tan
4
?
??
??
??
  (d) None of these 
Q 20.  A 50 Hz AC source of 20 V is connected across R and C as shown in figure. The voltage across R 
is 12 V. The voltage across C is 
 
Page 5


 
For JEE Advanced 
  Objective Questions 
  Single Correct Option 
Q 1.  A capacitor and resistor are connected with an AC source as shown in figure. Reactance of 
capacitor is X
C
 = 3? and resistance of resistor is 4 ?. Phase difference between current I and I
1
 is 
1o
3
tan 37
4
?
?? ??
?
?? ??
?? ??
 
 
  (a) 90°   (b) zero  (c) 53°   (d) 37° 
Q 2.  A circuit contains resistance R and an inductance L in series. An alternating voltage V = V
0
 sin ?t
 
is applied across it. The currents in R and L respectively will be 
 
 (a) I
R
 = I
0
 cos ?t, I
L
 = I
0
 cos ?t  (b) I
R
 = – I
0
 cos ?t, I
L
 = I
0
 cos ?t 
  (c) I
R
 = I
0
 sin ?t, I
L
 = - I
0
 cos ?t  (d) None of the above 
Q 3.  In the circuit shown in figure, the AC source gives a voltage V = 20 cos (2000t). Neglecting 
source resistance, the voltmeter and ammeter readings will be 
 
  (a) 0 V, 2.0 A   (b) 0 V, 1.4 A  (c) 5.6 V, 1.4 A  (d) 8 V, 2.0 A 
Q 4.  A signal generator supplies a sine wave of 200 V, 5 kHz to the circuit shown in the figure. Then 
choose the wrong statement 
 
  (a) The current in the resistive branch is 0.2 A 
  (b) The current in the capacitive branch is 0.126 A 
  (c) Total line current is ? 0.283 A 
  (d) Current in both the branches is same 
Q 5.  A complex current wave is given by i = (5 + 5 sin 100 ?t)A. Its average value over one time period 
is given as 
  (a) 10 A   (b) 5 A   (c) 50 A
   
(d) 0 
Q 6.  An AC voltage V = V
o
 sin 100t is applied to the circuit, the phase difference between
 
current and 
voltage is found to be ?/4, then 
 
 (a) R = 100 ?; C = 1 ?F   (b) R = 1k ?; C = 10 ?F  
  (c) R = 10k ?; L = 1H    (d) R = 1k ?; L = 10H 
Q 7.  In series L-C-R circuit voltage drop across resistance is 8 V, across inductor is 6 V and across 
capacitor is 12 V. Then 
  (a) Voltage of the source will be leading in the circuit 
  (b) Voltage drop across each element will be less than the applied voltage 
  (c) Power factor of the circuit will be 3/4 
  (d) None of the above 
Q 8.  Consider an L-C-R circuit as shown in figure, with an AC source of peak value V
o
 and angular
 
frequency ?. Then the peak value of current through the AC source is 
 
 (a) 
0
2
2
V
11
L
RC
??
? ? ?
??
?
??
    (b) 
2
0 2
11
VC
RL
?? ??
? ? ?
?? ??
?
?? ??
 
  (c) 
0
2
2
V
1
RL
C
??
? ? ?
??
?
??
    (d) None of these  
Q 9.  The adjoining figure shows an AC circuit with resistance R, inductance L and source voltage V
s
. 
Then 
 
  (a) the source voltage V
s
 = 72.8 V 
  (b) the phase angle between current and source voltage is tan
-1
(7/2) 
  (c) Both (a) and (b) are correct 
  (d) Both (a) and (b) are wrong 
Q 10.  When an alternating voltage of 220 V is applied across a device P, a current of 0.25 A flows 
through the circuit and it leads the applied voltage by an angle ?/2 radian. When the same voltage 
source is connected across another device Q, the same current is observed in the circuit but in 
phase with the applied voltage. What is the current when the same source is connected across a 
series combination of P and Q ? 
  (a) 
1
42 
A lagging in phase by ?/4
 
with voltage 
  (b) 
1
42 
A leading in phase by ?/4
 
with voltage 
  (c) 
1
2 
A leading in phase by ?/4 with voltage 
  (d) 
1
42 
A leading in phase by ?/2
 
with voltage 
Q 11.  In a parallel L-C-R circuit as shown in figure if I
R
 , I
L
, I
C
 and I represents the rms values of current 
flowing through resistor, inductor, capacitor and the source, then choose the appropriate correct 
answer 
 
  (a) I = I
R
+I
L
+I
C     
(b) I = I
R
+I
L 
-I
C
 
  (c) I
L
 or I
C
 may be greater than I  (d) None of the above 
Q 12.  In the AC network shown in figure, the rms current flowing through the inductor and capacitor are 
0.6 A and 0.8 A respectively. Then the current coming out of the source is 
 
  (a) 1.0A  (b) 1.4 A  (c) 0.2 A   (d) None of the above 
Q 13.  The figure represents the voltage applied across a pure inductor. The diagram which correctly 
represents the variation of current i with time t is given by 
 
  (a) (b)  (c)  (d)
y
 
Q 14.  In a series L-C-R circuit, current in the circuit is 11 A when the applied voltage is 220 V. Voltage 
across the capacitor is 200 V. If value of resistor is 20 ?,
 
then the voltage across the unknown 
inductor is 
  (a) zero   (b) 200V   (c) 20 V   (d) None of these 
Q 15.  A steady current of magnitude I and an AC current of peak value I are allowed to pass through 
identical resistors for the same time. The ratio of heat produced in the two resistors will be 
  (a) 2 : 1   (b) 1 : 2   (c) 1:1    (d) None of these 
Q 16.  In the circuit shown in figure, the power consumed is 
 
  (a) zero   (b) 
2
0
V
2R   
(c) 
2
0
2 2 2
VR
2(R L ) ??
  
(d) None of these 
Q 17.  In a series LC circuit, the applied voltage is V
o
. If ? is very low, then the voltage drop
 
across the 
inductor V
L
 and capacitor V
C
 are 
 
 (a) 
00
LC
VV
V ;V
22
??  (b) V
L
 = 0; V
C
 = V
0
 (c) V
L
 = V
0
; V
C
 = 0 (d) V
L
 = -V
C
 = 
0
V
2
 
Q 18.  A coil, a capacitor and an AC source of rms voltage 24 V are connected in series. By varying the 
frequency of the source, a maximum rms current of 6 A is observed. If coil is connected to a dc 
battery of emf 12 volt and internal resistance 4?, then current through it in steady state is 
  (a) 2.4 A   (b) 1.8 A  (c) 1.5 A   (d) 1.2 A 
Q 19.  In a series CR circuit shown in figure, the applied voltage is 10 V and the voltage across capacitor 
is found to be 8 V. The voltage across R, and the phase difference
 
between current and the applied 
voltage will respectively be 
 
 (a) 
1
4
6V, tan
3
?
??
??
??
  (b) 
1
3
3V, tan
4
?
??
??
??
  (c) 
1
3
6V, tan
4
?
??
??
??
  (d) None of these 
Q 20.  A 50 Hz AC source of 20 V is connected across R and C as shown in figure. The voltage across R 
is 12 V. The voltage across C is 
 
  (a) 8 V   (b) 16 V  (c) 10 V 
  (d) Not possible to determine unless value of R and C are given 
Q 21.  An AC voltage source described by V = 10 cos ( ?/2)
 
is connected to a 1 ?F
 
capacitor as shown in 
figure. The key K is closed at t = 0 s. The time (t > 0) after which the magnitude of current I 
reaches its maximum value for the first time is 
 
  (a) 1s    (b) 2s   (c) 3 s    (d) 4 s 
Q 22.  An AC voltage source V = V
0
 sin ?t
 
is connected across resistance R and capacitance C as shown 
in figure. It is given that R = 1/ ?C. The peak current is I
0
. If the angular frequency of the voltage 
source is changed to /3 ?
 then the new peak current in the circuit is 
 
 (a) 
0
I
2
    (b) 
0
I
2
   (c) 
0
I
3
   (d) 
0
I
3
 
Passage : (Q. No. 23 to 25) 
A student in a lab took a coil and connected it to a 12 VDC source. He measures the steady state 
current in the circuit to be 4 A. He then replaced the 12 V DC source by a 12 V, ( ? = 50 rad/s) AC 
source and observes that the reading in the AC ammeter is 2.4 A. He then decides to connect a 
2500 ?F capacitor in series with the coil and calculate the average power developed in the circuit. 
Further he also decides to study the variation in current in the circuit (with the capacitor and the 
battery in series). 
  Based on the readings taken by the student answer the following questions. 
Q 23.  The
 
value of resistance of the coil calculated by the student is 
 (a) 3 ?   (b) 4 ?   (c) 5 ?   (d) 8? 
Q 24.  The power developed in the circuit when the capacitor of 2500 ?F
 
is connected in series with the 
coil is  
  (a) 28.8 W   (b) 23.04 W  (c) 17.28 W   (d) 9.6 W 
Q 25.  Which of the following graph roughly matches the variations of current in the circuit (with the coil 
and capacitor connected in the series) when the angular frequency is decreased from 50 rad/s to 25 
rad/s? 
  (a) (b) (c)  (d) 
Passage : (Q. No. 26 to 28) 
It is known to all of you that the impedance of a circuit is dependent on the frequency of source. In 
order to study the effect of frequency on the impedance, a student in a lab took 2 impedance boxes 
P and Q and connected them in series with an AC source of variable frequency. The emf of the