Question

In an $L-R$ circuit connected to a battery of constant e.m.f $E$, switch S is closed at time t = 0. If e denotes the magnitude of induced e.m.f across inductor and i the current in the circuit at any time t. Then which of the following graphs shows the variation of $e$ with $i$ ?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

According to the Kirchoff's circuit law
$\frac{Ldi}{dt}=E-iR$ (straight line with - ve slope)
$e=E-iR$
$y=-Rx+C$
$(\therefore e=L\frac{di}{dt})$