Question

A metal disc of radius $100cm$ is rotated at a constant angular speed of $60rad{s}^{-1}$ in a plane at right angles to an external field of magnetic induction $0.05Wb{m}^{-2}$ . The emf induced between the centre and a point on the rim will be

• A. $3\text{ V}$
• B. $1.5\text{ V}$
• C. $6\text{ V}$
• D. $9\text{ V}$

Answer 1

Answer: (B)

Emf induced between the centre and a point on the rim due to a rotating disc is given by, $e=\frac{1}{2}B\omega R^2$
where, $B=$ External field of a magnetic induction,
$\omega =$ Angular speed of rotation and
$R=$ Radius of disc.
So, $e=\frac{1}{2}\left(0.05\right)\left(60\right){\left(1\right)}^2=1.5V$