Question

A copper disc of radius 5 cm is rotating in magnetic field B= 0.2 Gauss with 20 rev./sec. What will be a potential difference across the periphery and center of the disk:

• A. $20\pi \mu V$
• B. $10\pi \mu V$
• C. $\pi \mu V$
• D. $5\pi \mu V$

Answer 1

The correct option is C $\pi \mu V$

$B=0.2Gauss=0.2\times {10}^{-4}Tesla$

$w=20rev/sec=(20\times 2\pi )rad/sec$

$r=5cm=\frac{5}{100}meter$

Emf induced $=\frac{1}{2}Bw{R}^2$

$=\frac{1}{2}\times 0.2\times {10}^{-4}\times (20\times 2\pi )\times (\frac{5}{100}{)}^2=100\times {10}^{-8}Volt=\pi \mu V$