Question

A metallic rod of 1 m length is rotated with a frequency of 50 revolution per second, with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius 1 m about an axis passing through the centre and perpendicular to the plane of the ring. A constant uniform magnetic field of 1 T parallel to the axis is present everywhere. The emf between the centre and the metallic ring is:

• A. 157 V
• B. 117 V
• C. 127 V
• D. 137 V

Answer 1

Answer: (A)

157 V

Formula for E is

$E=\frac{1}{2}B\omega l^2=\frac{1}{2}\times 2\pi \times 50\times 1\times 1\times 2=50\pi =157V$