Question

A metal disc of radius $100 \,cm$ is rotated at a constant angular speed of $60$ rad/s in a plane at right angles to an external field of magnetic induction $0.05\, Wb/m^2$. The emf induced between the centre and a point on the rim will be

• A. 3 V
• B. 1.5 V
• C. 6 V
• D. 9 V

Answer 1

Answer: (B)

1.5 V

Answer 2

Induced emf produced between the centre and a point on the disc is given by $e = \frac{1}{2}\omega BR^{2}$ Putting the values, $\omega = 60rad/s,\, B=0.05\, Wb/m^{2}$ and $R = 100\, cm = 1m$ We get $e = \frac{1}{2} \times60\times 0.05\times \left(1\right)^{2} = 1.5V$