Question

Magnetic flux passing through a coil is initially 6 x 10^-4 Wb. It reduces to 10 % of its original value in 't' second. If the e.m.f. induced is 0.54 mV then 't' in second is ____________.

Options

• 1

• 0.4

• 0.5

• 0.6

Answer 1

Magnetic flux passing through a coil is initially 6 x 10^-4 Wb. It reduces to 10 % of its original value in 't' second. If the e.m.f. induced is 0.54 mV then 't' in second is 1.

Explanation:

`phi_1 = 6 xx 10^-4  "Wb"`

`phi_2 = 0.1 phi_1 = 0.6 xx 10^-4  "Wb"`

`therefore "d"phi = abs (phi_2 - phi_1) = 5.4 xx 10^-4  "Wb"`

dt = t second

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

`therefore 0.54 xx 10^-3`

` = (5.4 xx 10^-4)/"t"`

`therefore "t" = (5.4 xx 10^-4)/(0.54 xx 10^-3)`

`therefore "t" = 1  "second"`