O-LevelPhysicsMagnetism5054/22 · Oct/Nov 2020 · Q915 Marks

Fig. 9.1 shows a permanent magnet lying on a piece of paper. [Figure 9.1]

(a)Underline the material in the list from which it is possible to make a strong, permanent magnet. aluminium copper glass iron mercury plastic steel[1]
(b)Describe an experiment to plot the pattern and the direction of the magnetic field surrounding the magnet. You may draw on Fig. 9.1, if you wish.[4]
(c)Fig. 9.2 shows the N-pole of a magnet placed in front of the S-pole of a second magnet. [Figure 9.2] A section of a horizontal, metal wire JK lies in the magnetic field between the two magnetic poles. End K of the metal wire is connected to the positive terminal of a battery and end J is connected to the negative terminal.
(c)(i)Explain in terms of electrons, why there is a current in the wire and state the direction of the conventional current.[2]
(c)(ii)The part of JK that is in the magnetic field experiences a force F. State the direction of F and describe how this direction is deduced.[4]
(c)(iii)The equipment in Fig. 9.2 is used in a similar experiment. The part of JK that lies between the poles of the magnets, now passes through a long iron tube that is fixed in position. The tube is shown in Fig. 9.3. [Figure 9.3] JK is connected to the battery in the same way as before. State what happens to force F on the wire. Explain your answer.[2]
(d)The iron tube and the wire JK are removed. A square, vertical coil is placed between the poles so that the plane of the coil lies in the magnetic field as shown in Fig. 9.4. [Figure 9.4] Explain why the coil tries to rotate when there is a current in the coil.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[1] (a) steel underlined and no other material indicated
[1] (b) use of (plotting) compass
[1] (b) place the (plotting) compass (on the paper next to the magnet) and mark a dot where the compass needle points
[1] (b) move compass / other end of needle next to the dot and mark a dot where the compass needle points
[1] (b) continue and needle points in the direction of the magnetic field
[1] (c)(i) (free) electrons attracted to K/positive terminal or repelled by J/negative terminal
[1] (c)(i) (conventional current) from K to J or from positive or to negative or from right or to left
[1] (c)(ii) (Fleming) left-hand rule mentioned or equivalent rule mentioned
[1] (c)(ii) magnetic field related to index / pointer finger/equivalent
[1] (c)(ii) current related to middle finger / equivalent
[1] (c)(ii) thumb points down the page/ equivalent and force down (the page)
[1] (c)(ii) or catapult field explanation: field lines clockwise when viewed from K or anticlockwise when viewed from J
[1] (c)(ii) extra field lines / stronger field above wire
[1] (c)(ii) fewer field lines / weaker field below wire
[1] (c)(ii) force towards weaker field
[1] (c)(iii) there is no force F or it disappears/becomes equal to zero
[1] (c)(iii) wire is magnetically screened / shielded by the iron tube
[1] (d) moment acts (on coil) or forces (on vertical sides) in opposite directions
[1] (d) currents (in vertical sides) or in opposite directions
[1] (d) or coil becomes / acts as a magnet or coil produces magnetic field
[1] (d) N face (of coil) attracted to S pole (of magnet) or S face (of coil) attracted to N pole (of magnet) or N face (of coil) repelled by N pole (of magnet) or S face (of coil) repelled by N pole (of magnet))