Question

The self induced emf of a coil is 25 volts. When the current in it is changed at uniform rate from 10 A to 25 A in 1 s, the change in the energy of the inductance is ______.

Options

• 740 J

• 437.5 J

• 540 J

• 637.5 J

Answer 1

The self induced emf of a coil is 25 volts. When the current in it is changed at uniform rate from 10 A to 25 A in 1 s, the change in the energy of the inductance is 437.5 J.

Explanation:

According to faraday's law of electromagnetic induction,

e = `(-"d"phi)/"dt"`

`"L"xx"di"/"dt"` = 25 

⇒ `"L"xx15/1` = 25 

or L = `5/3`H

Change in the energy of the inductance,

ΔE = `1/2"L"("i"_1^2-"i"_2^2)`

= `1/2xx5/3xx(25^2-10^2)`

= `5/6xx525`

= 437.5 J