Magnetic Field Patterns

IGCSE Edexcel Physics
6.1–6.7 Permanent magnets, magnetic forces and field patterns
Key Concepts: Magnets have a north and south pole. Like poles repel; unlike poles attract. Magnetic field lines run from north to south outside a magnet and show the direction of force on a north pole. Closer field lines indicate a stronger field. Iron filings or a plotting compass can map field patterns.

Section A — Magnets and Magnetic Forces

1. State the rule for the interaction between magnetic poles. [2]
2. State the difference between a permanent magnet and an induced magnet. [2]
3. List three magnetic materials. [3]

Section B — Magnetic Field Lines

4. State what the direction of a magnetic field line represents. [1]
5. Describe the shape of the magnetic field around a bar magnet. Include the pattern at the poles and between the poles. [3]
6. Describe the field pattern between two unlike (N–S) poles placed close together. [2]
7. Describe the field pattern between two like (N–N) poles placed close together. [2]

Section C — Mapping Magnetic Fields

8. Describe how to use iron filings to show the magnetic field pattern around a bar magnet. [3]
9. Describe how to use a plotting compass to trace a magnetic field line from one pole of a bar magnet to the other. [3]
10. Two magnets are placed with their unlike poles facing each other with a small gap. Describe the field in the region between them. [2]

Total marks: 23

Mark Scheme

1. Like poles repel [1]; unlike poles attract [1] [2]
2. A permanent magnet retains its magnetism without being near another magnet [1]; an induced magnet is only magnetic when near a permanent magnet and loses magnetism when removed [1] [2]
3. Any three: iron, steel, nickel, cobalt [3]
4. The direction a free north pole would move (direction of force on a north pole) [1]
5. Field lines emerge from the north pole and enter the south pole [1]; they curve around the outside of the magnet [1]; the lines are closest together (most dense) at the poles, showing the field is strongest there [1] [3]
6. Field lines run from the N pole to the S pole across the gap [1]; the field in the middle of the gap is approximately uniform (parallel, evenly spaced lines) [1] [2]
7. Field lines push away from both poles [1]; there is a neutral point between the two poles where field lines cancel [1] [2]
8. Place paper over the bar magnet [1]; sprinkle iron filings evenly over the paper [1]; gently tap the paper so filings align along field lines to reveal the pattern [1] [3]
9. Place the compass near one pole and mark the direction the needle points [1]; move the compass to the marked point and repeat [1]; join the marks to trace the complete field line from one pole to the other [1] [3]
10. Uniform field — parallel, evenly spaced field lines running from N to S across the gap [2]