Question

What is the emf induced in a coil of $200 $ turns and cross sectional area $0.2 m ^{2}$, when a magnetic field perpendicular to the plane of the coil changes from $0.1 Wbm ^{-2}$ to $0.5 Wbm ^{-2}$ at a uniform rate over a period of $0.05$ sec ?

• A. $300\, V$
• B. $320\, V$
• C. $310\, V$
• D. $290\, V$

Answer 1

Answer: (B)

$e =?, N =200, A =0.2 m ^{2}$,
$B _{1}=0.1 Wbm ^{-2}$
$B _{2}=0.5 Wbm ^{-2}, t =0.05$ sec
$e =\frac{-\left(\phi_{2}-\phi_{1}\right)}{ t }$
$\Rightarrow \frac{- NA \left( B _{2}- B _{1}\right)}{ t }$
$\Rightarrow \frac{-200 \times 0.2(0.5-0.1)}{0.05}$
$e =-320 V$