**Alternating Current MCQs**

The current whose magnitude and direction reverses periodically is known as alternating current. The current produced from AC generator i.e. induced current is nothing but alternating current whose magnitude depends upon the frequency of rotation of coil.

The frequency of alternating current is number of rotation of coil per unit time. On the basis of rotation of coil the magnitude of current reverses from positive to negative and so on. Domestic electric current in India has the frequency of 50 cycles/second. The equation of alternating current is given as,

**R.M.S. current:**

It is defined as the value of steady current that would dissipate the same power in a given resistance as that by the alternating current.

**Q.1) The current whose magnitude and direction reverses periodically is known as…**

a) direct current

b) alternating current

c) induced current

d) none of these

**Q.2) Which among the following represents the correct form of alternating current?**

**Q.3) The current flowing through the circuit is given as, = 5 sin 10π t, peak value and angular frequency is SI system respectively will be….**

a) 5 A, 10 rad/s

b) 10 A, 5 rad/s

c) 5 A, 10 π rad/s

d) 5π A, 10 rad/s

**Q.4) Frequency of current in the following equation, i=4 sin 6π t A is…..Hz**

a) 1

b) 2

c) 3

d) 4

here 2πf=6π

∴ f = 3 Hz

**Q.5) RMS value of current in given current i=20 sin 3π t is……**

a) 2√2 A

b) 5√2 A

c) 10√2 A

d) 20√2 A

**Q.6) If coil rotates at the rate of 50 cycles/sec, the angular frequency for the current is…**

a) 100π

b) 50π

c) 25π

d) 4π

**Q.7) The rms value of current in an ac circuit is 30 A, then peak current is**

a) 42.42 mA

b) 42.42 A

c) 4.24 A

d) 424 A

**Q.8) The setup that converts an alternating current into direct current is known as……….**

a) DC generator

b) Half wave rectifier

c) Full wave rectifier

d) Both ‘b’ and ‘c’

**Q.9) If the peak values of alternating emf and alternating current are 50 V, 25 A respectively, the resistance of the circuit is….Ω**

a) 1

b) 2

c) 3

d) 4

**Q.10) The magnitude of peak value of current in circuit if the rms value of current is 12 A will be…..A**

a) 15

b) 16

c) 17

d) 18

**Answers:**

Q.1) b) alternating current

Q.2) a)

Q.3) c) 5 A, 10 π rad/s

Q.4) c) 3

Q.5) c) A

Q.6) a) 100π

Q.7) b) 42.42 A

Q.8) d) Both ‘b’ and ‘c’

Q.9) b) 2

Q.10) a) 15