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An A.C. circuit containing only capacitance, the
current : 
1. lags the voltage by 90°
2. leads the voltage by 90°
3. remains in phase with voltage
4. leads the voltage in 180°

A choke coil has: 
1. Low inductance and low resistance
2. High inductance and high resistance
3. Low inductance and high resistance
4. High inductance and low resistance

Turn ratio in a step-up transformer is 1: 2 if a
Lechlanche cell of 1.5 V is connected across the
input, then the voltage across the output will be:
1. 0.1 V     
2. 1.5 V 
3. 0.75 V 
4. zero

In the circuit shown below what will be the
reading of the voltmeter and ammeter ? 
(Total impedance of circuit Z = 100$\mathrm{\Omega }$)

1. 200 V, 1A
2. 800 V, 2A
3. 100 V, 2A
4. 220 V, 2.2 A

In a circuit the coil of a choke : 
1. decreases the current
2. increases the current
3. has high resistance to D. C. circuit
4. no effect with the current

In a circuit, the current lags behind the voltage
by a phase difference of p /2, the circuit will
contain which of the following : [2001]
1. only R
2. only C
3. R and C
4. only L

The coefficient of mutual inductance, when
magnetic flux changes by 2 × 10^–2 Wb and
current changes by 0.01 A is 
1. 8 henry
2. 4 henry
3. 3 henry
4. 2 henry

In an ideal parallel LC circuit, the capacitor is
charged by connecting it to a D.C. source which
is then disconnected. The current in the circuit:
1. becomes zero instantaneously 
2. grows monotonically
3. decays monotonically
4. oscillates instantaneously

A capacitor of capacitance 2µF is connected in
the tank circuit of an oscillator oscillating with a
frequency of 1 kHz. If the current flowing in the
circuit is 2 m A, the voltage across the capacitor
will be : 
1. 0.16 V
2. 0.32 V
3. 79.5 V
4. 159 V

A 50 Hz a.c. source of 20 volt is connected across
R and C as shown in figure. The voltage across
R is 12 volt. The voltage across C is : 

1. 8 V
2. 16 V
3. 10 V
4. not possible to determine unless values of
    R and C are given

In an AC circuit the potential differences across
an inductance and resistance joined in series
are respectively 16 V and 20 V. The total potential
difference of the source is [2007]
1. 20.0 V
2. 25.6 V
3. 31.9 V
4. 53.5 V

With the decrease of current in the primary coil
from 2 amperes to zero value in 0.01s the emf
generated in the secondary coil is 1000 volts.
The mutual inductance of the two coils is
1. 1.25 H
2. 2.50 H 
3. 5.00 H
4. 10.00 H

An AC source of angular frequency $\mathrm{\omega }$ is fed
across a resistor R and a capacitor C in series.
The current registered is I. If now the
frequency of source is changed to $\mathrm{\omega }$/3 (but
maintaining the same voltage), the current in
the circuit is found to be halved. Calculate
the ratio of reactance to resistance at the
original frequency $\mathrm{\omega }$
1. $\sqrt{\frac{3}{5}}$
2. $\sqrt{\frac{2}{5}}$
3. $\sqrt{\frac{1}{5}}$
4. $\sqrt{\frac{4}{5}}$

If an AC main supply is given to be 220 V. The
average emf during a positive half cycle will be
1. 198 V
2. 220 V 
3. 240 V
4. 220 $\sqrt{2}$V

A coil has an inductance of 0.7 henry and is
joined in series with a resistance of 220 $\mathrm{\Omega }$. When
the alternating emf of 220 V at 50 Hz is applied to
it then the phase through which current lags
behind the applied emf and the wattless
component of current in the circuit will be
respectively 
1. 30°, 1 A
2. 45°, 0.5 A
3. 60°, 1.5 A
4. none of these

An inductor and a resistor in series are
connected to an A.C. supply of variable
frequency. As the frequency of the source is
increased, the phase angle between current and
the potential difference across L will: 

1. first increase and then decrease
2. first decrease and then increase
3. go on decreasing
4. go on increasing

In a AC circuit the voltage and current are
described
by       V = 200sin$\left(319\mathrm{t}- \frac{\mathrm{\pi }}{6}\right)$ volts
and     i = 50sin$\left(314\mathrm{t}+ \frac{\mathrm{\pi }}{6}\right)$ mA
respectively. The average power dissipated in
the circuit is :
1. 2.5 watts
2. 5.0 watts
3. 10.0 watts
4. 50.0 watts

If we decrease the frequency of the applied A.C. with a purely capacitive load, do (1) the amplitude of V${}_{\mathrm{c}}$ and (2) amplitude of I${}_{\mathrm{c}}$increase, decrease of remain the same. 
1. (1) increase (2) same
2. (1) same (2) increase
3. (1) same (2) decrease
4. (1) decrease (2) same

An inductor coil of inductance L is cut into two
equal parts and both the parts are connected in
parallel. The net inductance is : [2011]
1. L
2. L/2
3. L/4
4. 2 L.

The current in resistance R at resonance is

1. zero 
2. minimum but finite
3. maximum but finite
4. infinite