Page 431 - Physics Coursebook 2015 (A level)

Chapter 26: Magnetic fields and electromagnetism
5 Figure 26.28 shows a wire XY which carries a constant direct current. Plotting compass R, placed alongside the wire, points due north. Compass P is placed below the wire and compass Q is placed above the wire.
X P
Q
Y
N
R
S
Figure 26.28 For End-of-chapter Question 5.
a State the direction of the current in the wire. [2]
b State in which direction compass P points. [2]
c State in which direction compass Q points if the current in the wire is reversed. [2]
6 Figure 26.29 shows a rectangular metal frame PQRS placed in a uniform magnetic field. 4.0 cm
QR
PS
2.5 A
4.5 × 10–3 T
7.0 cm
Figure 26.29 For End-of-chapter Question 6.
The magnetic flux density is 4.5 × 10−3 T and the current in the metal frame is 2.5 A.
a Calculate the force experienced by side PQ of the frame. [3]
b Suggest why side QR does not experience a force. [1]
c Describe the motion of the frame immediately after the current in the frame is switched on. [2]
d Calculate the maximum torque (moment) exerted about an axis parallel to side PQ. [2]
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