Question

An e.m.f. of 100 millivolts is induced in a coil when the current in another nearby coil becomes 10 ampere from zero in 0.1 second. The coefficient of mutual induction between the two coils will be

• A. 1 millihenry
• B. 10 millihenry
• C. 100 millihenry
• D. 1000 millihenry

Answer 1

Answer: (A)

1 millihenry

Answer 2

Induced

$e.m.f.\mspace{6mu}\mspace{6mu} e = M\frac{di}{dt} \Rightarrow 100 \times 10^{- 3} = M\left( \frac{10}{0.1} \right)$

$\therefore\mspace{6mu} M = 10^{- 3}H = 1\mspace{6mu} mH$