A coil has an inductance of 2.5 H and a resistance of 0.5 r. If the coil is suddenly connected across a 6.0 volt battery, then the time required for the current to rise 0.63 of its final value is 

(1) 3.5 sec

(2) 4.0 sec

(3) 4.5 sec

(4) 5.0 sec

Subtopic:  LR circuit |
 58%
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An inductance L and a resistance R are first connected to a battery. After some time the battery is disconnected but L and R remain connected in a closed circuit. Then the current reduces to 37% of its initial value in time ?

(1) RL sec

(2) RLsec

(3) LRsec

(4) 1LRsec

Subtopic:  LR circuit |
 78%
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In an LR-circuit, the time constant is that time in which current grows from zero to the value (where I0 is the steady-state current) 

(1) 0.63 I0

(2) 0.50 I0

(3) 0.37 I0

(4) I0

Subtopic:  LR circuit |
 76%
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A coil of wire having finite inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t = 0 so that a time-dependent current I1(t) starts flowing through the coil. If I2(t) is the current induced in the ring and B(t) is the magnetic field at the axis of the coil due to I1(t), then as a function of time (t > 0), the product I2 (t) B(t

(1) Increases with time

(2) Decreases with time

(3) Does not vary with time

(4) Passes through a maximum

Subtopic:  LR circuit |
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The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is 10 Ω. The current in the circuit will be:

1. i = 0.5 A

2. i > 0.5 A

3. i < 0.5 A

4. i = 0

Subtopic:  LR circuit |
From NCERT
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The figure shows three circuits with identical batteries, inductors, and resistors. Rank the circuits according to the current, in descending order, through the battery (i) just after the switch is closed and (ii) a long time later:

1. \((i) i_2>i_3>i_1\left(i_1=0\right) (ii) i_2>i_3>i_1\)
2. \((i) i_2<i_3<i_1\left(i_1 \neq 0\right) (ii) i_2>i_3>i_1\)
3. \((i) i_2=i_3=i_1\left(i_1=0\right)\left(\right. (ii) i_2<i_3<i_1\)
4. \((i) i_2=i_3>i_1\left(i_1 \neq 0\right) (ii) i_2>i_3>i_1\)
Subtopic:  LR circuit |
 71%
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The network shown in the figure is a part of a complete circuit. If at a certain instant the current i is 5 A and is decreasing at the rate of 103 A/s then VB – VA is

(1) 5 V

(2) 10 V

(3) 15 V

(4) 20 V

Subtopic:  LR circuit |
 67%
From NCERT
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Switch S of the circuit shown in the figure is closed at t = 0. If e denotes the induced emf in L and i denotes the current flowing through the circuit at time t, then which of the following graphs is correct?

1.  2.
3. 4.
Subtopic:  LR circuit |
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The current in an L – R circuit builds up to (3/4)th of its steady state value in 4 seconds. The time constant of this circuit is

1. 1In 2sec                                                2. 2In 2sec

3. 3In 2sec                                                4. 4In 2sec

Subtopic:  LR circuit |
 57%
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An emf of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time t = and at t = 1 second is-

1. e1/2e1/2-1                                           2. e2e2-1

3. 1-e-1                                              4. e-1

Subtopic:  LR circuit |
 64%
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