Question

A coil is placed in transverse magnetic field of $0.02\, T$. This coil starts shrinking at a rate of $1 \,mm / \sec$. when its radius is $4\, cm$, then what is the value if the induced emf.

• A. $2\, \mu V$
• B. $2.5\, \mu V$
• C. $5\, \mu V$
• D. $8 \,\mu V$

Answer 1

Answer: (C)

induced emf =-rate of change of magnetic flux
$e=-d / d t(B A)=B x d A / d t$
$=-3.14 \times 0.02 \times(2 \times 0.04) \times\left(-10^{-3}\right)$
$=5 \times 10^{-6}=5\, \mu V$.