Question 1

Paper 2Medium8 marks

A coil has 120 turns and an area of 4.0×10−3 m24.0\times10^{-3}\,\text{m}^2 It is in a uniform magnetic field of 0.20 T0.20\,\text{T} The angle θ\theta is measured between the field and the normal to the coil.

Initially, θ=60∘\theta=60^\circ The coil rotates steadily until θ=0∘\theta=0^\circ taking 0.10 s0.10\,\text{s} The magnetic field remains constant during this rotation.

(a)

Calculate the magnetic flux through one turn of the coil initially.

[1]
(b)

Determine the magnitude of the average induced emf during the rotation.

[3]
(c)

The same rotation from θ=60∘\theta=60^\circ to θ=0∘\theta=0^\circ is now completed in 0.25 s0.25\,\text{s} Calculate the magnitude of the average induced emf and explain how it compares with your answer to (b).

[2]
(d)

The coil is held stationary with its normal parallel to the field. The magnetic field decreases uniformly from 0.20 T0.20\,\text{T} to 0.12 T0.12\,\text{T} in 0.050 s0.050\,\text{s} Determine the magnitude of the average induced emf.

[2]

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