A rectangular wire loop of sides 8 cm and 3 cm, with a small cut, is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the plane of the loop. The emf developed across the cut, if the velocity of the loop is 2 cm s⁻¹ in a direction normal to the shorter side of t…

Question

A rectangular wire loop of sides 8 cm and 3 cm, with a small cut, is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the plane of the loop. The emf developed across the cut, if the velocity of the loop is 2 cm s⁻¹ in a direction normal to the shorter side of the loop, will be:

Accepted Answer

(4) 1.8×10⁻⁴ volt. The emf is ε=Bℓ v, where ℓ is the length of the side that cuts across the field lines. The loop moves normal to the shorter side, so it is the 3 cm side that sweeps out new area and sets the emf; the 8 cm sides run along the motion and contribute nothing. ε=0.3×(3×10⁻²)×(2×10⁻²)=1.8×10⁻⁴ V. Picking the wrong side is the whole trap here: 8 cm would give 4.8×10⁻⁴ V.

Step-by-step solution

Why the other options are wrong