Question 1
The figure below shows a solenoid connected to a battery. At points P and Q,
Earth has a horizontal magnetic field comparable in size to that produced by the solenoid at these points. a. Draw and arrow at point P to indicate the direction of the magnetic field at that point.
1 mark b. Roget has a small magnet that is free to rotate about an axis at its centre.
This is shown below. In this question, ignore the effect of Earth’s magnetic field.
Roger places the magnet at point Q. Identify which of the following best shows the orientation that the magnet will take.
1 mark

Question 2
Two identical bar magnets of the same strength are arranged at right angles and are equidistant from point P, as show below.
For the first part of this question only ignore Earth’s magnetic field. a. At point P on the diagram, draw an arrow indicating the direction of the combined magnetic field of the bar magnets.
1 mark
The bar magnets are replaced by two weaker magnets. The two new magnets are identical to each other. They are arranged at right angles and are equidistant from point P.
The magnitude of a single bar magnet at point P is the same as the magnitude of the magnetic field of the Earth at point P. The direction of the Earth’s magnetic field is shown below. b. At point P on the diagram, draw an arrow indicating the direction of the combined magnetic field of the bar magnets and the earth.
2 marks

Question 3
The figure below shows a diagram of a DC electric motor. The motor has a rectangular coil, JKLM or 50 turns. The two permanent magnets provide a uniform magnetic field of 0.30 T in the region of the coil. a. A current I is flowing through the rectangular coil in the direction shown.
Draw an arrow on side JK to show the direction of the magnetic force on side JK.
1 mark b. A current of 6.0 A is flowing in the 50-turn rectangular coil. The length of side JK is 5.0 cm. Calculate the magnitude of the magnetic force acting on side
JK.
2 marks
Question 4 a. Complete the diagram by sketching five magnetic field lines around the magnet. You must include arrows which show the direction of the magnetic field of the magnet.
2 mark
A second bar magnet is placed next to the original as shown below. b. Complete the diagram by sketching magnetic field lines to indicate the shape of the magnetic field around the magnets.
3 marks

Question 5
A 10cm section of a conducting wire is placed in a uniform magnetic field a shown below. A DC current of I = 1.0 A produces a force of 0.01 N on the wire. a.
Draw an arrow to indicate the direction of the magnetic force on the wire.
1 mark b. What is the strength of the magnetic field between the magnets?
2 marks c.
The wire is now connected to an AC power source with frequency 100 Hz instead of a DC source. Briefly explain what happens to the wire and why.
2 marks

Question 6
Thomas is trying to build a simple motor that will operate on DC current. He first decides to study the magnetic forces on a current-carrying wire. He places a single loop of wire in a uniform magnetic field, and connects a batters, as shown below. a.
What direction indicates the direction of the magnetic field at point x?
1 mark b. What direction indicates the direction of the magnetic field at point y?
1 mark c. What direction indicates the direction of the magnetic field at point z?
1 mark d. What direction indicates the direction of the magnetic field at point w?
1 mark

Question 7
A vertical wire carrying current I is placed opposite the centre of a permanent bar magnet as shown. a. Which of the arrows (A-F) best shows the direction of the magnetic force on the wire at point P?
2 marks b. Which is the arrows (A-F) best shows the direction of the magnetic force acting on the north pole of the magnet due to the wire?
2 marks

Question 8
The figure below shows a power line at a mining site that carries a current of
2000A running from west to east. The Earth’s magnetic field at the mining site is
4.0 × 10 −5 T, running horizontally from south to north.
An engineer is concerned about the electromagnetic force due to the Earth’s magnetic field on the wire between the two support poles, which are 20 m apart. a.
Calculate the magnitude and direction (north, south, east, west, up, down) of the force due to the Earth’s magnetic field on the 20 m section of wire between the two poles.
3 marks

Question 9
The figure below shows a coil of wire connected to a battery. The plane of the coil is perpendicular to the page. a. Draw five magnetic field lines to show the direction of the magnetic field through the coil.
2 marks

Question 10
The figure below shows a magnet with pole pieces that are each 40cm x 10 cm.
The uniform magnetic field strength between the poles is 2.0 × 10 −3 T and zero outside the poles. A conducting wire, AB, carrying a current of 5.0 A, is placed between the poles as shown. The force on the wire is upwards. a.
In what direction, AB or BA, is the current flowing in the wire? b.
What is the magnitude of the force on the wire?
2 marks
2 marks

Question 11
The figure below shows a diagram of a simple DC motor. The single square loop coil TUVW, os side 0.0090 M, is free to rotate about the axis XY. Current is supplied from a battery and two permanent magnets provide a uniform magnetic field B of magnitude 0.25 T in the region of the coil. The current flowing in the coil is 2.0 A. a.
Indicate with an arrow the direction of the force on side TU of the coil in the figure above.
1 mark b. Calculate the magnitude of the force on the side TU of the coil.
2 marks c.
Calculate the magnitude of the force of on the side UV of the coil.
2 marks