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CBSE

Subject

Physics

NEET Physics : Alternating Current

Multiple Choice Questions

31.

The rms speed (in m/s) of oxygen molecules of the gas at temperature 300 K, is

32.

Real power consumption in a circuit is least when it contains.

high R, low L
high R, high L
low R, high L
high R, low C

33.

In an L-C-R circuit inductance is changed from L to L/2.To keep the same resonance frequency, C should be changed to

2 C
$\frac{C}{2}$
4 C
$\frac{C}{4}$

34.

220 V, 50 Hz, AC source is connected to an inductance of 0.2 Hand a resistance of 20 Ω in series. Whatis the current in the circuit?

3.33 A
33.3 A
5 A
10 A

35.

In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is

$\frac{1}{2 πf (2 πf L + R)}$
$\frac{1}{πf (2 πf L + R)}$
$\frac{1}{2 πf (2 πf L - R)}$
$\frac{1}{πf (2 πf L - R)}$

36.

In a series L-C-R circuit, resistance R = 10 Ω and the impedance Z = 10 Ω. The phase difference between the current and the voltage is

0^o
30^o
45^o
60^o

37.

Induced emf in the coil depends upon

conductivity of coil
amount of flux
rate of change of linked flux
resistance of coil

38.

If we change the value of R, then

voltage does not change on L
voltage does not change on LC combination
voltage does not change on C
voltage changes on LC combination

39.

A choke is preferred to a resistance for limiting current in AC circuit because

choke is cheap
there is no wastage of power
choke is compact in size
choke is a good absorber of heat

40.

The impedance of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f, is

$\sqrt{R + 2 π^{2} f^{2} L^{2}}$
$\sqrt{R + 4 π^{2} f^{2} L^{2}}$
$\sqrt{R^{2} + 4 π^{2} f^{2} L^{2}}$
$\sqrt{R^{2} + 2 π^{2} f^{2} L^{2}}$

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