Question

Magnetic flux passing through a coil is initially 4 × 10^-4 Wb. It reduces to 10% of its original value in t second. If the emf induced is 0. 72 mV then t in second is ______.

पर्याय

• 0.3

• 0.4

• 0.5

• 0.6

Answer 1

Magnetic flux passing through a coil is initially 4 × 10^-4 Wb. It reduces to 10% of its original value in t second. If the emf induced is 0. 72 mV then t in second is 0.5.

Explanation:

We have given,

Initial flux (Φ₁) = 4 × 10^-4 Wb

Final flux (Φ₂) = `(4xx10^-4xx10)/100`

= 4 × 10^-5 Wb

Emf induced (e) is given by

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

⇒ 0.72 × 10^-3 = `(4xx10^-4-4xx10^-5)/"t"`

⇒ t = `(4xx10^-5xx9)/(72xx10^-5)` 

= `1/2`

0.5 S