Question

Q79. A coil of 100 turns is linked to by a
magnetic flux of 20mWb. If this flux is
reversed in a time of 2 ms,the average e.m.f
induced in the coil is :
(A) 20 volt
(B) 2000 volt
(C) 200 volt
(D) 2 volt​

Answer 1

Solution :

As per the given data ,

• No of turns = 100
• Ф i  = 20 m Wb = 20 x 10^-3 Wb

• Ф f = 20 m Wb = - 20 x 10^-3 Wb

• Time = 2 x 10^-3 s

The EMF induced in the coil is given by the formula ,

$\leadsto \boxed{E = - n \times \dfrac{\Delta \phi}{t}}$

Here , negative sign denotes that EMF is opposing in nature .

Now let us substitute the given values in the above equation ,

$\leadsto E = - 100 \times \dfrac{(-20 - 20)\times 10^{-3}}{2 \times 10^{-3}}\\ \\ \leadsto E = - 100 \times \dfrac{- 40 \times 10^{-3}}{2 \times 10^{-3}}\\ \\ \leadsto E = - 100 x - 20 \\ \\ \leadsto\boxed{ E = 2000 V }$

The average EMF induced in the coil is 2000 V.