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

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. $\frac{R}{L}sec$

3. $\frac{L}{R}sec$

4. $\frac{1}{LR}sec$

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

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:

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 V_B – V_A is

1. 5 V

2. 10 V

3. 15 V

4. 20 V