Alternating Current Mcqs

This set of Multiple choice questions and answers focuses on study of Alternating Current in Physics. These questions are chosen from a collection of most authoritative and best reference books on Physics. Our aim is to prepare an individual for competitive exams like NTS, GAT, ECAT, MDCAT, Teaching jobs Tests and Chemical industry job interviews. One should practice our Mcqs to assimilate knowledge on Alternating Current in Physics comprehensively.

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1.
A 100?F capacitor with 12V source in series having frequency 50Hz will offer a capacitive reactance of about

32?

62?

50?

100?

2.
A 10? electric heater is connected to a 220V 50Hz mains supply. What is the peak value of the potential difference across the heater element?

220V

220/ ??2V

110V

220 ??2V

3.
A capacitor of capacitance 30?F is charged by a constant current of 10mA. If initially the capacitor was uncharged what is the time taken for the potential difference across the capacitor to reach 300V?

0.9sec

15 sec

1.5x105sec

0.9x102sec

4.
A changing magnetic flux produces around itself an induced

Magnetic field

Electric field

Electromagnetic force

Artificial gravitational field

5.
A choke is used as a resistance in

DC circuit

AC circuits

Both AC and DC circuit

Full wave rectifier circuit

6.
A pure variable resistor is connected in series with a pure capacitor of fixed capacitance. The impedance of the circuit

Remains

Becomes infinite

Becomes zero

Increases

7.
a voltage V = V? cos ?t is applied across a resistor of resistance R the average power dissipated per cycle in the resistor is given by

V?/?2R

V?/?2?R

V?2/?2R

V?2/?2?R

8.
A wire of resistance R is coiled inductively so that its inductance is L. The impedance of the coil at a frequency of f is

(R+2?fL)

R+1/2?fL

(R2+f2L2)

(R2+4?2f2L2)

9.
Ammeter connected in an AC circuit measures

Exact value of current

Rms value of current

Net value of current

Peak value of current

10.
An A.C series circuit containing 4? resistance and 3-? inductive reactance. The impedance of the circuit is

1?

5?

7?

7/?2?

11.
An alternating current is represented by the equation I = I?sin?t which of the following equation represents an alternating current of frequency and amplitude twice that of the above current?

I = 2I?Sin(?t/2)

I = 2I?Sin(2?t)

I = 2ISin?t

I = I?sin(2?t)

12.
An alternating current of r.m.s value of 2A and a steady direct current I flowing through identical resistors dissipate heat at the same rate. What is the current I?

2A

A

13.
An alternating current of r.m.s value of 4.0 A and frequency 50Hz flows in a circuit containing 10? resistor. The peak current is then

20A

20.66A

6.66A

5.66A

14.
An alternating current or voltage

Fluctuates off and on

Varies in magnitude alone

Changes its direction again and again

Changes its magnitude harmonically and reverses its direction of flow after regularly recurring intervals.

15.
An alternating potential difference is connected across a pure resistor and the frequency of the supply is varied but the rms value of the voltage is kept constant. The mean rate of heat dissipated from the resistor is

Directly proportional to f

Directly proportional to ??f

Directly proportional to f2

Inversely proportional to f

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