Alternating Current

For a given series LCR circuit it is found that maximum current is drawn when value of variable capacitance is 2.5 nF. If resistance of 200 and 100 mH inductor is being used in the given circuit. The frequency of ac source is 103 Hz (given 2 = 10)

An ac source is connected in given series LCR circuit. The rms potential difference across the capacitor of 20 is V. [figure]

A series LCR circuit is subjected to an ac signal of 200 V, 50 Hz. If the voltage across the inductor (L = 10 mH) is 31.4 V, then the current in this circuit is .

1. 10 A
2. 10 mA
3. 68 A
4. 63 A

In an ac circuit, the instantaneous current is zero, when the instantaneous voltage is maximum. In this case, the source may be connected to : Choose the correct answer from the options given below :

1. A, B and C only
2. A and B only
3. A, B and D only
4. B, C and D only

An alternating current at any instant is given by i= [6+ 56 (100 t+ /3) ] A. The rms value of the current is A.

Match List I with List II Choose the correct answer from the options given below:

1. A-IV, B-I, C-III, D-II
2. A-I, B-IV, C-II, D-III
3. A-IV, B-I, C-II, D-III
4. A-I, B-IV, C-III, D-II

In series LCR circuit, the capacitance is changed from C to 4C. To keep the resonance frequency unchanged, the new inductance should be:

1. increased by 2 L
2. reduced by 14 L
3. reduced by 34 L
4. increased to 4 L

A transformer has an efficiency of 80\% and works at 10 V and 4 kW. If the secondary voltage is 240 V, then the current in the secondary coil is :

1. 1.33 A
2. 13.33 A
3. 1.59 A
4. 15.1 A

An AC voltage V=20 200 t is applied to a series LCR circuit which drives a current I=10 (200 t+ 3 ). The average power dissipated is:

1. 21.6 W
2. 200 W
3. 173.2 W
4. 50 W

Primary coil of a transformer is connected to 220 V ac. Primary and secondary turns of the transformer are 100 and 10 respectively. Secondary coil of transformer is connected to two series resistances shown in figure. The output voltage (V0) is : [figure]

1. 7 V
2. 44 V
3. 22 V
4. 15 V