Alternating Current MCQs
1. What is the frequency of a 5μF capacitor that has a reactance of 1000 Ω?
a) 200 cycle/sec
b) 100/π cycle/sec
c) 5000 cycles/sec
d) 1000/π cycles/sec
Answer: (b) 100/π cycle/sec
2. What is the reciprocal of impedance?
a) Admittance
b) Inductance
c) Reactance
d) Conductance
Answer: (a) Admittance
3. What is the time taken by the alternating current of 50 Hz with an r.m.s value of 10 ampere to reach from zero to a maximum value and the peak value of current?
a) 2×10-2 sec and 14.24 amp
b) 5 ×10-3 sec and 8.07 amp
c) 5×10-3 sec and 14.14 amp
d) 1×10-2 sec and 7.07 amp
Answer: (c) 5×10-3 sec and 14.14 amp
4. What is the voltage applied across the resonant circuit if the ac voltage across resistance R, inductance L and capacitance C is 5 V, 10 V and 10 V respectively?
a) 5 V
b) 10 V
c) 20 V
d) 25 V
Answer: (a) 5 V
5. Why can’t the DC ammeter measure an alternating current?
a) AC cannot pass through a DC ammeter
b) AC changes its direction
c) AC is virtual
d) The average value of a complete cycle is zero
Answer: (d) The average value of a complete cycle is zero
6. What is the frequency of ac mains in India?
a) 120 Hz
b) 60 Hz
c) 50 Hz
d) 30 Hz
Answer: (c) 50 Hz
7. What is the peak value of the voltage of an electric lamp connected to a 220 V, 50 Hz supply?
a) 311 V
b) 320 V
c) 211 V
d) 210 V
Answer: (a) 311 V
