Question

If in a coil rate of change of area is 5 m²/milli second and current become 1 amp from 2 amp in $2 \times 10^{- 3}sec.$ If magnitude of field is 1 tesla then self inductance of the coil is

• A. 2 H
• B. 5 H
• C. 20 H
• D. 10 H

Answer 1

Answer: (D)

10 H

Answer 2

$N\varphi = Li \Rightarrow \frac{Nd\varphi}{dt} = \frac{Ldi}{dt} \Rightarrow NB\frac{dA}{dt} = \frac{Ldi}{dt}$

$\Rightarrow \frac{1 \times 1 \times 5}{10^{- 3}} = L \times \left( \frac{2 - 1}{2 \times 10^{- 3}} \right) \Rightarrow L = 10H$