Question

A metal disc of radius $200 cm$ is rotated at a constant angular speed of $60 rad s ^{-1}$ in a plane at right angles to an external field of magnetic induction of $0.05 Wbm ^{-2}$. Find the emf induced between the center and a point on the rim.

• A. $12\, V$
• B. $8\, V$
• C. $2\, V$
• D. $6\, V$

Answer 1

Answer: (D)

$e = BAv \Rightarrow B.A \times \frac{\omega}{2 \pi}$
$\Rightarrow B \times \pi R ^{2} \times \frac{\omega}{2 \pi}$
$e=\frac{1}{2} B R^{2} \omega$
$\Rightarrow \frac{1}{2} \times 0.05 \times(2)^{2} \times 60=6$ volt