MCQs of Alternating Current

Alternating Current MCQs

MCQs of Alternating Current

Showing 141 to 150 out of 168 Questions

141.

The inductance of the motor of a fan is 1.0 H. To run the fan at 50 Hz, the capacitance of the capacitor that will cancel out its inductive reactance will be _____

(a)	10 μF
(b)	40 μF
(c)	0.4 μF
(d)	0.04 μF

142.

An L - C - R series an A.C. circuit is tuned to resonance. The impedance of the circuit is now _____

(a)	${[R^{2 +} {(ω L)}^{2} + {(\frac{1}{ω C})}^{2}]}^{\frac{1}{2}}$
(b)	${[R^{2} + {(ω L - \frac{1}{ω C})}^{2}]}^{\frac{1}{2}}$
(c)	R
(d)	${[R^{2} + {(\frac{1}{ω C} - ω L)}^{2}]}^{\frac{1}{2}}$

143.

Resonant frequency of an L-C-R series an A.C. circuit is

f_{0}

. Now, the capacitance is made 4 times, then the new resonance frequency will become _____

(a)	$f_{0}$
(b)	$\frac{f_{0}}{2}$
(c)	$\frac{f_{0}}{4}$
(d)	$2 f_{0}$

144.

In an A.C. circuit, a resistance of R Ohm is connected in series with an inductor of self inductance L. If phase angle between voltage and current be

45^{o}

, then the value of inductive reactance

(X_{L})

wil be equal to _____

(a)	$\frac{R}{4}$
(b)	$\frac{R}{2}$
(c)	R
(d)	$\frac{R}{8}$

145.

Find the time required for a 50 Hz alternating current to become from zero to its r.m.s. value.

(a)	15.0 ms
(b)	10.0 ms
(c)	5.0 ms
(d)	2.5 ms

146.

What is the average power dissipation in an ideal capacitor in an A.C. circuit ?

(a)	zero
(b)	$2 C V^{2}$
(c)	$C V^{2}$
(d)	$\frac{1}{2} C V^{2}$

147.

In an series resonant circuit, an A.C. voltage across resistance R, inductor L and capacitor C are 5 V, 10 V and 10 V respectively. An A.C. voltage applied to the circuit will be _____

(a)	5 V
(b)	10 V
(c)	20 V
(d)	25 V

148.

A coil has self inductance L=0.04 H and resistance R=12 Ohm. If it is connected to a 220 V, 50 Hz supply, then what will be the current through the coil ?

(a)	10.7 A
(b)	11.7 A
(c)	14.7 A
(d)	12.7 A

149.

Energy required to establish a current of 4 A in a coil of self inductance L=200 mH is _____

(a)	1.6 J
(b)	0.40 J
(c)	0.18 J
(d)	0.16 J

150.

The quantity that remains unchanged in the output with respect to the input in an ideal transformer is _____

(a)	voltage
(b)	frequency
(c)	currnt
(d)	None of the above

Showing 141 to 150 out of 168 Questions