A flat search coil of area 2 cm² and 25 turns is normal to a magnetic field, then quickly removed or rotated 90°. Total charge through the coil is 7.5 mC and total resistance is 0.50 Ω. Estimate B.
Physics · Electromagnetic Induction
JEE Advanced

Question

A flat search coil of area 2 cm² and 25 turns is normal to a magnetic field, then quickly removed or rotated 90°. Total charge through the coil is 7.5 mC and total resistance is 0.50 Ω. Estimate B.

G1 Physics · Accepted Answer

Magnetic flux is Φ=∫B⃗·dA⃗ and induced emf is ε=−dΦ/dt. Apply Lenz’s law for direction and I=ε/R when the circuit is resistive. This gives 0.75.