Question

Assertion(A): An insulator rod is moving uniformly in a transverse uniform field, induced EMF is zero across the rod. Reason(R): In insulator there are no free electrons.

• A. (A) is correct & (R) is correct & (R) is correct explanation for (A)
• B. (A) is correct & (R) is correct & (R) is not correct explanation for (A)
• C. (A) is correct & (R) is incorrect
• D. (A) is incorrect & (R) is correct

Answer 1

Answer: (D)

(A) is incorrect & (R) is correct

Answer 2

Motional EMF in a rod moving with velocity $\vec{v}$ in a magnetic field $\vec{B}$ is given by $\mathcal{E} = \int (\vec{v} \times \vec{B}) \cdot d\vec{l}$. The Lorentz force $\vec{F} = q(\vec{v} \times \vec{B})$ acts on all charges, free or bound. In an insulator, while there are no free electrons to form a current, the Lorentz force still causes charge separation, creating a potential difference (EMF) across the rod. Thus, Assertion (A) is incorrect. Reason (R) is correct as insulators lack free electrons.