Question

An LR circuit with a battery is connected at t = 0. Which of the following quantities is not zero just after the connection?

Options

• Current in the circuit

• Magnetic field energy in the inductor

• Power delivered by the battery

• Emf induced in the inductor

Answer 1

Emf induced in the inductor

 

At time t = 0, the current in the L-R circuit is zero. The magnetic field energy is given by `U=1/2Li^2,` as the current is zero the magnetic field energy will also be zero. Thus, the power delivered by the battery will also be zero. As, the LR circuit is connected to the battery at t = 0, at this time the current is on the verge to start growing in the circuit. So, there will be an induced emf in the inductor at the same time to oppose this growing current.