Question

In the circuit shown in figure initially the switch is in position 1 for a long time then suddenly at $t=0$, the switch is shifted to position 2. It is required that a constant current should flow in the circuit, the value of resistance $R$ in the circuit

• A. should be decreased at a constant rate
• B. should be increased at a constant rate
• C. should be maintained constant
• D. Not possible

Answer 1

Answer: (D)

Not possible

In steady state,
$i=\frac{E}{R}$
to maintain the current const.
after the switch changes position
$L\frac{di}{dt}-iR=0$
If $i=const.$
$\frac{di}{dt}=o$
which gives
$iR=0$
$E=0$
Not possible