Alternating Current Applied to an Inductor

Q.

A $40\mu F$ capacitor is connected to a $200V,50Hz$ ac supply. The RMS value of the current in the circuit is, nearly:

1. $1.7A$

2. $2.05A$

3. $2.5A$

4. $25.1A$

Q. A choke coil has

1. High inductance and low resistance
2. Low inductance and high resistance
3. High inductance and high resistance
4. Low inductance and low resistance

Q. Choke coil is used to control

1. ac
2. dc
3. Both ac and dc
4. Neither ac nor dc

Q. An inductor and a resistor are connected in series with an AC source. In this circuit

1. current and potential difference across the resistor lead the potential difference across the inductor.
2. current and potential difference across the resistor lag behind the potential difference across the inductor by an angle $\frac{\pi }{2}$.
3. current and potential difference across the resistor lag behind the potential difference across the inductor by an angle $\pi$.
4. potential difference across the resistor lags behind the potential difference across the inductor by an angle $\frac{\pi }{2}$ but the current in the resistor leads the potential difference across the inductor by an angle $\frac{\pi }{2}$.

Q. An inductor of inductance $L=5H$ is connected to an AC source having voltage $V=10\sin \left(10t\right)$. What is the value of peak current?

1. $\frac{1}{2}A$
2. $\frac{1}{3}A$
3. $\frac{1}{4}A$
4. $\frac{1}{5}A$

Q. Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be

1. Increases in the first circuit and decreases in the other
2. Increases in both the circuits
3. Decreases in both the circuits
4. Decreases in the first circuit and increases in the other

Q.

The voltage across an inductor is given by

1. $v=-L\frac{di}{dt}$

2. $v=L\frac{di}{dt}$

3. $v=-L\frac{dt}{di}$

4. $v=L\frac{dt}{di}$

Q. In a given R-L A.C circuit, if peak voltage of the source is 10 V, and peak voltage across resistance is 6 V, then what is the voltage across inductor when voltage the across resistance is 3V? ($\sqrt{(}3)=1.732$)

Q. When $100$ volt dc is appiled across a coil, a current of 1 amp flows through it. When $100V$ A.C of $50Hz$ is appiled to the same coil, only $0.5$ amp flows. What is the value of inductance of the coil ?

1. $\frac{\sqrt{3}}{\pi }H$
2. $\frac{\pi }{\sqrt{3}}H$
3. $\frac{\sqrt{2}}{\pi }H$
4. $\frac{\pi }{\sqrt{2}}H$

Q. The magnetic field energy in an inductor changes from maximum value to minimum value in 5.0 ms when connected to an AC source, . The frequency of the source is

1. 20 Hz
2. 50 Hz
3. 200 Hz
4. 500 Hz

Q. Two resistors are connected in series across a $5\text{V rms}$ source of alternating potential. The potential difference across $6\Omega$ resistor is $3\text{V}$. If R is replaced by a pure inductor $L$ of such magnitude that current remains same, then the potential difference across $L$ is

1. $1\text{V}$
2. $2\text{V}$
3. $3\text{V}$
4. $4\text{V}$

Q. A series RC circuit has $R=50\Omega$ and C = 20 mF. Find the time at which the current is half the steady state value.

1. ln (3) s
2. ln (5) s
3. 2 s
4. ln (2) s

Q. In the section shown $i=(3t^2-2t)A$. Find $V_A-V_B$ at t = 1s

1. 0 V
2. 10 V
3. 20 V
4. 14 V