Page 461 - Physics Coursebook 2015 (A level)

Chapter 28: Electromagnetic induction
7 Figure 28.32 shows a square coil about to enter a region of uniform magnetic field of magnetic flux density 0.30 T. The magnetic field is at right angles to the plane of the coil. The coil has 150 turns and each side is 2.0 cm in length. The coil moves at a constant speed of 0.50 m s−1.
2.0 cm
0.50 m s–1
B
uniform magnetic field (into plane of paper)
2.0 cm
coil with 150 turns
Figure 28.32 For End-of-chapter Question 7.
a i Calculate the time taken for the coil to completely enter the region of magnetic field. [1] ii Determine the magnetic flux linkage through the coil when it is all within the region of magnetic field. [2]
b Explain why the induced e.m.f. is constant while the coil is entering the magnetic field. [1]
c Use your answer to a to determine the induced e.m.f. across the ends of the coil. [4]
d What is the induced e.m.f. across the ends of the coil when it is completely within the magnetic field?
Explain your answer. [2]
e Sketch a graph to show the variation of the induced e.m.f. with time from the instant that the coil
enters the magnetic field. Your time axis should go from 0 to 0.08 s. [2]
8 a
b A circular coil of diameter 200 mm has 600 turns (Figure 28.33). It is placed with its plane perpendicular
State Faraday’s law of electromagnetic induction. [2] to a horizontal magnetic field of uniform flux density 50 mT. The coil is then rotated through 90° about
a vertical axis in a time of 120 ms.
axis
coil
Figure 28.33 For End-of-chapter Question 8.
Calculate:
i the magnetic flux passing through the coil before the rotation [2]
ii the change of magnetic flux linkage produced by the rotation [2]
iii the average e.m.f. induced in the coil during the rotation. [2]
449