Alternating current

Written by Dr. Hamza Farooq (Physics)

Class 12 · Physics · 8 questions

Name: ____________________   Date: ____________

1. The rms value of an AC with peak value 10 A is:

   • A 14.1 A
   • B 7.07 A
   • C 10 A
   • D 5 A

2. In a purely resistive AC circuit, the current and voltage are:

   • A 180 degrees apart
   • B 90 degrees apart
   • C Unrelated
   • D In phase

3. Capacitive reactance is given by:

   • A 2 pi f L
   • B 2 pi f C
   • C 1 / (2 pi f L)
   • D 1 / (2 pi f C)

4. Inductive reactance:

   • A Increases with frequency
   • B Decreases with frequency
   • C Is zero always
   • D Does not change

5. At resonance in a series LCR circuit, the impedance is:

   • A Infinite
   • B Minimum and equal to R
   • C Maximum
   • D Zero

6. The frequency of mains AC in Pakistan is:

   • A 50 Hz
   • B 25 Hz
   • C 100 Hz
   • D 60 Hz

7. A choke coil reduces AC with little loss of power because it has high:

   • A Capacitance
   • B Mass
   • C Resistance
   • D Inductive reactance

8. The power factor of a purely resistive circuit is:

   • A 0.5
   • B 1
   • C 0
   • D Infinite