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An alternating voltage E = 200 sin 300 t is applied across a series combination of R = 10 Ω and an inductor 800 mH. The power factor of the circuit is

(A)

0.022

(B)

0. 065

(C)

0.042

(D)

0. 084

Question-2

The inductance of a coil is directly proportional to

(A)

its length

(B)

the number of turns

(C)

the resistance of the coil

(D)

the square of the number of turns

Question-3

The time constant of C - R circuit is

(A)

1/CR

(B)

C/R

(C)

CR

(D)

R/C

Question-4

A 100 mH coil carries a current of 1 A. Energy stored in the magnetic field is

(A)

0.5 J

(B)

I J

(C)

0.1 J

(D)

0.05 J

Question-5

A L-C circuit is in a state of resonance. If C = 0.1 μF and L = 0.25 H, then neglecting the ohmic resistance of the circuit, find the frequency of oscillations.

(A)

1007 Hz

(B)

100 Hz

(C)

109 Hz

(D)

500 Hz

Question-6

A rectangular coil of 20 turns and area of cross-section 25 cm^{2} has a resistance of 100 Ω. If a magnetic field which is perpendicular to the plane of the coil changes at the rate of 1000 T per second, the current in the coil is

(A)

1 A

(B)

50 A

(C)

0. 5 A

(D)

5 A

Question-7

Energy needed to establish an alternating current I in a coil of self inductance L is

(A)

L di/dt

(B)

Zero

(C)

LI^{2}/2

(D)

IL^{2}/2

Question-8

In an AC circuit, the rms value of current, i_{rms} is related to the peak current, i_{0} by the relation

(A)

i_{rms} = √2i_{0}

(B)

i_{rms} = πi_{0}

(C)

i_{rms} = i_{0}/π

(D)

i_{rms} = 1/√2 i_{0}

Question-9

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately

(A)

30%

(B)

50%

(C)

90%

(D)

10%

Question-10

An alternating voltage V = 200√2 sin (100t) is connected to a 1μF capacitor through an AC ammeter. The reading of the ammeter shall be

(A)

10 m

(B)

20 mA

(C)

40 mA

(D)

80 mA

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