Exams › JEE Advanced › Physics

A rectangular coil lies in a region of uniform magnetic field B that is perpendicular to the plane of the coil. In which of the following situations will NO emf be induced in the coil?

1. the magnetic field is increased uniformly
2. the magnetic field is switched off
3. the coil is rotated about the axis XX' (an in-plane axis)
4. the coil is rotated about an axis perpendicular to the plane of the coil passing through its centre O

Correct answer: the coil is rotated about an axis perpendicular to the plane of the coil passing through its centre O

Solution

Induced emf requires a change in flux phi = B*A*cos(angle). Increasing or switching off B changes B and hence flux (emf induced). Rotating about an in-plane axis XX' changes the angle between the area vector and B, so flux changes (emf induced). But rotating about the axis perpendicular to the coil's plane keeps the area vector parallel to B and the enclosed area unchanged, so flux is constant and no emf is induced.

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 →