Exams › JEE Advanced › Physics

An L-R circuit connected to a battery is switched on at t = 0. Immediately after the switch is closed, which of the following quantities is NOT zero?

1. current in the circuit
2. magnetic energy stored in the inductor
3. power delivered by the battery
4. emf induced in the inductor

Correct answer: emf induced in the inductor

Solution

Just after switching on, the inductor prevents an instantaneous jump in current, so the current is zero at t = 0+. Therefore the magnetic energy (1/2 L i²) is zero, and power delivered by the battery (V*i) is zero. However, the inductor develops a back-emf equal to the full battery emf at that instant (since L*di/dt is maximum and equals V), so the induced emf is non-zero.

Related JEE Advanced Physics questions

• What is the final velocity attained by the loop?
• A long coaxial cable is made up of two cylindrical conductors with radii a and b. The inner conductor carries a constant current i, while the outer conductor acts as the return path for the current. What is the self-inductance of a segment of the cable of length l?
• Determine the inductance per unit length for a loop created by connecting the ends of two infinitely long parallel wires, each with radius r, and separated by a distance d between their centers. Ignore the magnetic flux inside the wires and the effects at the ends.
• If the electromotive force is 10 V and the rate of change of current is calculated as 2.5 A/s, what is the self-inductance of the coil, given by L = e / (dl/dt)?
• The magnitude of the induced electric field in the orbit at any instant of time during the time interval of the magnetic field change is
• A semicircular loop of radius r is positioned on the axis of a large current-carrying circular ring of radius R (with R >> r). The loop is placed at an axial distance of R*sqrt(3) from the center of the ring, and the plane of the semicircular loop makes an angle of 53 deg with the plane of the ring. Find the mutual inductance M between the two coils.

⚔️ Practice JEE Advanced Physics free + battle 1v1 →