1. 1
   A student is investigating the poles of two bar magnets, A and B, on a laboratory bench. She places them end to end, close together but not touching, and observes what happens each time she changes their orientation.

   (a)

   Two bar magnets are placed end to end on a bench, close together but not touching. The north pole of magnet A faces the south pole of magnet B. A student then turns magnet B around so that its north pole now faces the north pole of magnet A. Which row correctly describes the two situations?

   [1 mark]

   • AOriginally: attract; after turning: attract
   • BOriginally: attract; after turning: repel
   • COriginally: repel; after turning: attract
   • DOriginally: repel; after turning: repel

   (b)

   The student now wants to identify the north pole of magnet B without touching it to another magnet. Which method would correctly identify the north pole?

   [1 mark]

   • ASuspend magnet B freely so it can turn; the end that settles pointing towards the Earth's geographic north is the magnet's north pole
   • BMeasure the mass of magnet B; the heavier end is the north pole
   • CHeat magnet B gently; the end that warms up fastest is the north pole
   • DPlace magnet B in water; the end that floats higher is the north pole

   (c)

   The student says magnet A is a permanent magnet and a nearby steel paperclip becomes an induced magnet when magnet A is brought close to it. Explain the difference between a permanent magnet and an induced magnet, and state what happens to the paperclip's magnetism when magnet A is removed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician is building a demonstration electromagnet for a school open day. She wraps insulated wire around different core materials and tests how strongly each one attracts steel pins, both while the current is flowing and immediately after it is switched off.

   (a)

   A technician is choosing a material to make the core of an electromagnet that must lose its magnetism as soon as the current is switched off. Which pair of materials are both suitable choices for this core?

   [1 mark]

   • AIron and steel
   • BSteel and nickel
   • CIron and nickel
   • DCobalt and steel

   (b)

   The technician uses a plotting compass to investigate the magnetic field of a bar magnet placed on the bench, moving the compass to different positions around the magnet and marking the direction the needle points at each position. Which statement about this method is correct?

   [1 mark]

   • AThe compass needle always points away from the nearest pole of the magnet, regardless of which pole it is closest to
   • BThe compass only works if it is placed touching the magnet's surface
   • CThe compass needle points in a random direction at each position, so it cannot be used to map the field
   • DFollowing the direction the compass needle points at successive positions traces out a field line running from the magnet's north pole to its south pole

   (c)

   Describe, in words, the shape and direction of the magnetic field around a single bar magnet, and explain how the concentration of field lines shown by the plotting compass relates to the strength of the field at different points.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A geologist gives a talk to a physics class about the Earth's magnetic field. She hands round several compasses and asks the students to observe how the needles behave when carried to different corners of the classroom, and to think about what this tells us about the planet.

   (a)

   A geologist is explaining to a class why an ordinary magnetic compass can be used for navigation anywhere on the Earth's surface. Describe the evidence a compass provides that the Earth behaves like it has a giant bar magnet inside it, and state what this evidence suggests about the core of the Earth.

   [3 marks]

   (b)

   One student in the class suggests using a permanent bar magnet instead of a compass to find magnetic north, by holding the magnet on a piece of string until it stops swinging. Explain why this method would work, describing what happens to the magnet as it settles and why it always settles in the same orientation regardless of where in the room it is tested.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A manufacturer makes two very different magnetic products at the same factory: permanent fridge magnets (from steel or cobalt-iron alloy) and temporary electromagnetic lifting magnets used to move scrap metal in a scrapyard (soft iron cores wrapped in coils of wire).

   (a)

   A manufacturer produces fridge magnets from steel and separately from a cobalt–iron alloy, and also produces temporary lifting magnets used in scrapyards from soft iron cores wrapped in wire. Explain, using ideas about permanent and induced magnetism and about magnetic pole interactions, why steel and cobalt alloys are chosen for the fridge magnets while soft iron is chosen for the scrapyard lifting magnet, and describe how the fridge magnet's field allows it to hold objects to a fridge door.

   [6 marks]

   (b)

   The factory's quality inspector wants to check every batch of fridge magnets using only a plotting compass, without touching the magnets together. Describe a full method the inspector could use to map the shape and direction of the magnetic field around a fridge magnet with a plotting compass, and explain how the resulting pattern of field lines would let the inspector judge whether the magnet is faulty (for example, unusually weak).

   [6 marks]

   Total for question 4: 12 marks

End of questions