Question

In the circuit shown the cell is ideal. The coil has an inductance of 4H and zero resistance. F is a fuse of zero resistance and will blow when the current through it reaches 5A.The switch is closed at t = 0. The fuse will blow-

• A. After 5 sec
• B. After 2 sec
• C. After 10 sec
• D. Almost at once

Answer 1

Answer: (C)

After 10 sec

Answer 2

E = $L\frac{di}{dt}$

di = $\frac{E}{L}dt$

i = $\frac{E}{L}t$

i = $\frac{2}{4} \times t$

i = 0.5t

5 = 0.5t

t = 10 sec