Question

A current / = 1.5 A is flowing through a long solenoid of diameter 3.2 cm, having 220 turns per
cm. At its centre, a 130 turn closely packed coil of diameter 2.1 cm is placed such that the coi
is coaxial with the long solenoid. The current in the solenoid is reduced to zero at a steady rate
in 25 ms. What is the magnitude of emf induced in the coil while the current in the solenoid is
changing?

Answer 1

The magnitude of emf induced in the coil while the current in the solenoid is  changing is 75 mV.

Explanation:

Initially magnetic flux passing through the coil (one turn).

ϕ1 = B →.A → = B.Acos0∘ = μoml × πd^2 / 4

ϕ1 = 4π × 10^−7 × 1.5 × 22000 × 3.464 × 10^−4  

ϕ1 = 1.44 × 10^−5 Wb

Finally the flux becomes zero because the current reduces to zero.

Thus, e = |Δϕ| / Δt

= 1.44 × 10^−5 / 25 × 10^−3

= 5 .76 × 10^−4 V

The total emf = N × e = 130 × 5.76 × 10^−4

The total emf =75 mV

Thus the magnitude of emf induced in the coil while the current in the solenoid is  changing is 75 mV.

Also learn more

A 0.5 long solenoid of 10 turns/cm has area of cross section 1 cm2 cal voltage induced across its ends if the current in the solenoid changes from 1 ampere to 2 ampere in o. 1 sec  ?

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