Question 259: Electromagnetic Induction

Question

A magnetic field of $2 	imes 10^{-2} \mathrm{~T}$ acts at right angles to a coil of area $100 \mathrm{~cm}^2$ with 50 turns, The average e.m.f. induced in the coil is 0.1 V , when it is removed from the field in time $t$. The value of ' $t$ ' is (in second)

Accepted Answer

Using Lenz law,
Induced e.m.f. is given by, $e=-N \frac{\mathrm{~d} \phi}{\mathrm{dt}}\quad	ext{.... (i)}$
Change in magnetic flux $=\frac{\mathrm{d} \phi}{\mathrm{dt}}=\frac{\mathrm{dB}}{\mathrm{dt}} \mathrm{A} \cos 	heta$
From (i),
$$\begin{array}{rlrl} 
& e =-N \frac{d B}{d t} A \cos 	heta \
& 	herefore\quad e =-\frac{N\left(B_2-B_1ight) A \cos 	heta}{t} \
& 	herefore \quad t =\frac{-(50) 	imes\left(0-2 	imes 10^{-2}ight) 	imes\left(100 	imes 10^{-4}ight) 	imes \cos 0^{\circ}}{0.1} \
& 	herefore \quad t =0.1 \mathrm{~s}
\end{array}$$

Answer

0.1 s

Answer

0.01 s

Answer

1 s

Answer

20 s

Electromagnetic Induction

A magnetic field of 2 \times 10^{-2} \mathrm{~T} acts at right angles to a coil of area 100 \mathrm{~cm}^2 with 50 turns, The average e.m.f. induced in the coil is 0.1 V , when it is removed from the field in time t. The value of ' t ' is (in second)

Choose the correct answer: