Exams › JEE Main › Physics

Two identical coaxial circular current loops carry equal currents i flowing in the same sense. If the loops are moved closer together, what happens to the current in each loop (assuming each is part of a circuit maintaining the same conditions)?

1. the current in each will decrease
2. the current in each will increase
3. the current in each will remain the same
4. the current in one increases and in the other decreases

Correct answer: the current in each will decrease

Solution

As the loops approach, the mutual flux through each loop (due to the other, same-sense current) increases. By Lenz's law the induced EMF opposes this increase, i.e. it opposes the existing current, so the current in each loop decreases.

Related JEE Main Physics questions

• A metallic ring is kept in a horizontal position, and a bar magnet is released so that it falls through the ring with its length aligned along the ring’s axis. The magnet’s acceleration while falling is
• A coil has resistance 10 Ω, and the magnetic flux linked with it changes with time according to ϕ = 4t² + 2t + 1 (in weber). The current induced in the coil at t = 1 s is
• Two coils are kept near one another. The mutual inductance of the coil pair depends on
• A conducting rod of length ℓ is attached to a string of length 2ℓ and is rotated on a horizontal table about the fixed end of the string with angular speed ω. If a uniform magnetic field B acts vertically through the region, what is the induced emf between the two ends of the rod?
• A pair of coils, each having N turns, has mutual inductance M henry. If the current in one coil changes from 1 ampere to zero in time t seconds, what is the induced emf per turn in the other coil, in volts?
• A boat travels straight toward the east in a place where Earth’s magnetic field is horizontal, points due north, and has magnitude 5.0 × 10⁻⁵ N A⁻¹ m⁻¹. A 2 m long vertical antenna is mounted on the boat. If the boat’s speed is 1.50 m s⁻¹, what emf is induced across the antenna wire?

⚔️ Practice JEE Main Physics free + battle 1v1 →