Question

A magnetic Held of $2\times {10}^{-2}T$ acts at right angles to a coil of area 100 cm2 with 50 turns. The average emf induced in the coil is 0.1 V. When it is removed from the field in time r, the value of t is

• A. 0.1 s
• B. 0.01 s
• C. 1 s
• D. 10 s

Answer 1

Answer: (A)

Induced emf $e=-\frac{\Delta \varphi }{\Delta t}$ $e=-\frac{({\varphi }_2-{\varphi }_1)}{t}$ $=-\frac{(0-nBA)}{t}=\frac{nBA}{t}$ $\therefore$ $0.1=\frac{50\times 2\times {10}^{-2}\times 100\times {10}^{-4}}{t}$ $\Rightarrow$ $t=\frac{50\times 2\times {10}^{-2}\times 100\times {10}^{-4}}{0.1}$ $=0.1s$