Magnets, poles and magnetic fields
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A force you cannot see
- Poles and forces
- Magnetic materials
- The test for a magnet
Read the transcript of the teaching part
Last time
Before we start: last time, in Sound waves and the speed of sound, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
A force you cannot see
Hold two fridge magnets close, and you feel them push or pull, with nothing touching. A compass needle swings to point north. The force acts through empty space, in a region we call a magnetic field. By the end of this lesson you can draw it.
Poles and forces
A magnet has two poles, a north pole and a south pole. The poles are where the force is strongest. Like poles repel. Unlike poles attract. A freely hanging magnet turns until its north pole points to the north. That is why it is called the north-seeking pole.
Magnetic materials
Only a few materials are magnetic: iron, steel, nickel and cobalt. Copper, aluminium, wood and plastic are not attracted by a magnet. A magnet attracts these materials, but it only repels another magnet.
The test for a magnet
A magnet attracts a piece of iron, and also another magnet. So attraction alone does not show that something is a magnet. But repulsion only happens between two like poles. So repulsion is the proof of a magnet. Test: bring one end near each pole of a known magnet. Repelled by one of them means a magnet.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Magnetic fields and field lines · Magnetic fields and field lines · Magnetic poles and forces.
The whole chapter: Simple Phenomena of Magnetism, Simple Magnetism and Magnetic Fields.
Chapter 4.1: Simple magnetism and magnetic fields
- Magnets, poles and magnetic fields 5 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.