MCQs of Alternating Current

Alternating Current MCQs

MCQs of Alternating Current

Showing 71 to 80 out of 168 Questions

71.

The value of capacitive reactance of capacitor is X_C. If the values of the capacitance and frequency becomes double, the value of capacitive reactance becomes _____

(a)	4X_C
(b)	$\frac{X_{C}}{2}$
(c)	$\frac{X_{C}}{4}$
(d)	2X_C

72.

In L - C - R circuit, the energy dissipates in _____

(a)	L only
(b)	C only
(c)	R only
(d)	all of the above

73.

A L - C - R circuit connected to an A.C. source of frequency f. If current in phase leads by 45° then voltage, the capacitance of capacitor _____

(a)	$\frac{1}{2 π f (2 π f L - R)}$
(b)	$\frac{1}{2 π f (2 π f L + R)}$
(c)	$\frac{1}{π f (2 π f L - R)}$
(d)	$\frac{1}{π f (2 π f L + R)}$

74.

Usually in A.C. circuit _____

(a)	average current is zero.
(b)	average square velocity is zero.
(c)	dissipiation of average power is zero.
(d)	phase difference between voltage and current is zero,

75.

A L - C circuit contain 10 mH inductor and a 25 μF capacitor. The resistance of the circuit is negligible. The energy stored in the circuit is completely magnetic at time ( in milli seconds). The time is measured from the instant when the circuit is closed _____ ms.

(a)	1.57, 4.71, 7.85, ....
(b)	1.57, 3.14, 4.71, ....
(c)	0, 1.57, 4.71, ....
(d)	None of these

76.

The resistance of a coil for D.C. is in ohms. In A.C. the resistance _____

(a)	will remain same
(b)	will increase
(c)	will decrease
(d)	will be zero.

77.

If instantaneous current is given by i = 4 cos (ωt + Φ) ampere, than the rms value of current is ______ ampere.

(a)	4
(b)	$2 \sqrt{2}$
(c)	$4 \sqrt{2}$
(d)	zero

78.

A sinusoidal a.c. current flows through a resistor of resistance R Ω. If the peak current is I_p, then the power dissipated is _____ .

(a)	$I_{P}^{2} R \cos θ$
(b)	$\frac{1}{2} I_{P}^{2} R$
(c)	$\frac{4}{π} I_{P}^{2} R$
(d)	$\frac{1}{4} I_{P}^{2} R$

79.

An electric heater rated 220V and 550W is connected to A.C. mains. The current drawn by it is _____ amp.

(a)	0.8
(b)	2.5
(c)	0.4
(d)	1.25

80.

An alternating current is given by the equation i = (i₁cos ωt + i²sin ωt). The rms current is given by _____ .

(a)	$\frac{1}{\sqrt{2}} (i_{1} + i_{2})$
(b)	$\frac{1}{\sqrt{2}} (i_{1} + i_{2})^{2}$
(c)	$\frac{1}{\sqrt{2}} ({i_{1}}^{2} + {i_{2}}^{2})^{\frac{1}{2}}$
(d)	$\frac{1}{2} ({i_{1}}^{2} + {i_{2}}^{2})^{\frac{1}{2}}$

Showing 71 to 80 out of 168 Questions