Exams › JEE Main › Physics
A square conducting loop of side 10.0 cm lies perpendicular to a uniform magnetic field of 20 T. A 10 V bulb is connected in series with the loop. The field is reduced steadily to zero over a time interval deltaₜ. For what deltaₜ will the bulb shine at full brightness (i.e. the induced emf equals 10 V)?
- 20 ms
- 0.02 ms
- 2 ms
- 0.2 ms
Correct answer: 20 ms
Solution
The flux through the loop is B*A. As B falls to zero uniformly, the induced emf is A*B/deltaₜ. Setting this equal to the bulb's 10 V rating and solving gives deltaₜ.
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 →