Magnetism and fields covers how magnets and currents create magnetic fields, how a field is drawn, why iron becomes magnetic near a magnet, and how a field pushes on a wire that carries current. It is a short topic, but it rewards careful drawing and exact wording.
Exact requirements change between syllabus years, so check the current Cambridge IGCSE Physics 0625 page for your exam year. The Physics learning guide shows where this topic sits in the whole subject.
What do I need to know first?
You need the idea of a force (a push or pull with a direction) and the basics of a circuit: current flows round a loop, and conventional current runs from the positive terminal to the negative. The electrical energy and safe interpretation module covers circuits. No advanced maths is needed.
One worked example that previews the whole topic
A straight wire carries current into the page. It sits between a north pole on the left and a south pole on the right. (Invented situation for practice.)
Field direction: field lines run from north to south, so the field points left to right.
Force direction: use Fleming’s left-hand rule. First finger points along the field (right), second finger along the conventional current (into the page), and the thumb then gives the force. The thumb points downwards.
Changing one thing: if the current doubles and everything else stays the same, the force doubles. If the current is reversed, the force has the same size but points upwards.
Notice the three ideas at work: a field has a direction, a current has a direction, and the force depends on both.
In what order should I study the lessons?
- Sketch a field pattern with direction. Every later lesson uses field lines, so draw these first.
- Explain induced magnetism. This shows why a magnet attracts an unmagnetised nail, using the field you have just drawn.
- Compare permanent and temporary magnetic behaviour. It builds on induced magnetism and explains iron versus steel.
- Use a field-current-force relationship. This combines field direction, current direction and force.
- Interpret a magnetic test. It asks you to draw conclusions from results, using everything above.
Then use the magnetism and fields practice set to test all five together. The next module, induction and transformers, builds directly on this one.
What traps catch students?
- Arrows on field lines pointing into a north pole. They leave north and enter south.
- Field lines that cross or stop in empty space.
- Mixing up the hands. Fleming’s left-hand rule is for the force on a current. The right-hand grip rule is for the field made by a current.
- Using electron flow instead of conventional current in the hand rule.
- Claiming attraction proves a magnet. Only repulsion is a reliable test.
- Forgetting that soft iron and steel behave differently after the magnet or current is removed.
How do I use the practice set well?
Attempt it after the lessons, with a pencil for sketches. Write a short reason for each answer, then compare with the worked solution. The last section routes each kind of error back to the right lesson.
Drawing and reasoning habits are easier to fix with someone watching you work. Our teachers can do that in online one-to-one Physics tuition.