Q. When a certain circuit consisting of a constant e.m.f. $E,$ an inductance $L$ and a resistance $R$ is closed, the current in it increases with time according to curve 1. After one parameter$\ (E,\ L\ or\ R)\ $is changed, the increase in current follows curve 2 when the circuit is closed second time. Which parameter was changed and in what direction
A) $L$ is increased
B) $L$ is decreased
C) $R$ is increased
D) $R$ is decreased
Explanation
(a) $\frac{di}{dt} =$ slope of $i - t$ graph; slope of graph (2) < slope of graph (1) so $\left( \frac{di}{dt} \right)_{2} < \left( \frac{di}{dt} \right)_{1};$ Also $L \propto \frac{1}{(di/dt)} \Rightarrow L_{2} > L_{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.