Answer:
I = 2.19A, anticlockwise direction.
Explanation:
Given r = 33cm = 0.33m, N = 12, ΔB = 7.5 - 1.5 = 6.0T, Δt = 3s, R = 3.75Ω
By Faraday's law of electromagnetic induction when there is a change in flux in a coil or loop, an emf is induced in the coil or loop which is proportional to the time rate of change of the magnetic flux through the loop.
The emf E is related to the flux by the formula
E = – NdФ/dt
Where N = number of turns in the coil, Ф = magnetic flux through the loop = BA, B = magnetic field strength, A = Area
In this problem the strength of the magnetic field changes. As a result the flux too changes and an emf is induced in the coil.
So
ΔФ = ΔB×A = ΔB×πr² = 6×π×0.33² = 2.05Wb
E = -NΔФ/Δt = 12×2.05/3 = 8.2V
I = E/R = 8.2/ 3.75 = 2.19A
The direction of the current can be found by pointing the thumb of your right hand in the direction of the magnetic field and curling the remaining fingers around this direction. The direction of the curl of these fingers give the direction of current which in this case is anticlockwise.
