Unit 9: Magnetism and electromagnets
Magnetic fields — HIA International - Grade 7 Revision Notes & Topical Questions
5 min read 8 parts Lesson 2 of 5 3 quizzes
Lesson summary
Magnetic fields — HIA INTERNATIONAL notes: Describe magnets, magnetic materials and magnetic fields, and draw and interpret field lines.Magnet = an object that attracts magnetic materials.Magnetic materials — iron, steel, nickel and cobalt.Poles — a magnet has a north pole and a …
- Test for a magnet
- Non-magnetic metals
- Every magnet
- Strongest at the poles
- Stronger magnet
- Attraction
Section 1 of 8Magnets and magnetic materials
Magnet
Magnet an object that attracts magnetic materials.
Magnetic materials
- Magnetic materials iron, steel, nickel and cobalt.
Poles
- Poles a magnet has a north pole and a south pole, shown as N and S.
- Opposite poles attract.
- Like poles repel.
Test for a magnet
- Test for a magnet only repulsion proves an object is a magnet, because a magnet attracts any magnetic material.
Non-magnetic metals
- Non-magnetic metals copper, aluminium and zinc are not attracted.
Section 2 of 8The magnetic field
Magnetic field
Magnetic field the area around a magnet where the effects of the magnet can be detected.
Every magnet
- Every magnet is surrounded by a magnetic field.
Strongest at the poles
- Strongest at the poles the field of a magnet is strongest at its poles.
Distance
- Distance a paper clip is attracted only when it is inside the field; further away the force stops.
Stronger magnet
- Stronger magnet the field extends further and the lines are closer together.
Section 3 of 8Detecting a magnetic field
Attraction
- Attraction a magnetic object moves towards the magnet when it is in the field.
Compass
- Compass a compass contains a magnetised needle that turns to point along the field.
Iron filings
- Iron filings sprinkled on paper over a magnet they show the shape of the field.
Section 4 of 8Rules for magnetic field lines
Direction
- Direction the lines have arrows that point from the north pole to the south pole.
Join poles
- Join poles the lines join opposite poles.
No touching
- No touching field lines must not touch each other.
No crossing
- No crossing field lines must not cross each other.
Strength
- Strength the field is strongest where the lines are closest together.
Compass
- Compass a compass in the field points in the direction of the line.
Section 5 of 8Fields of two magnets
| Arrangement | Field lines between magnets | Force |
|---|---|---|
| N pole facing S pole | All point the same way | Attraction |
| N facing N or S facing S | Point in opposite directions | Repulsion |
Section 6 of 8Plotting a field with a compass
1
Place a bar magnet on a sheet of paper and draw around it.
2
Put a plotting compass near the north pole and mark where the needle points.
3
Move the compass so its tail is on the mark and mark the new needle position.
4
Repeat until the south pole is reached, then join the marks into a smooth line.
5
Add an arrow from north to south and repeat from other starting points.
Section 7 of 8Key terms
| Term | Meaning |
|---|---|
| Magnetic field | The area around a magnet where the effects of the magnet can be detected. |
| Magnetic material | A material attracted by a magnet, such as iron, steel, nickel or cobalt. |
| Pole | One of the two ends of a magnet, north or south, where the field is strongest. |
| Field line | A line showing the direction of a magnetic field, from north to south. |
| Compass | A freely turning magnetised needle that points along a magnetic field. |
| Iron filings | Tiny pieces of iron that show the pattern of a magnetic field. |
Section 8 of 8Exam technique
1
Attraction proves an object is a magnet — only repulsion does, because a magnet also attracts magnetic materials.
2
Field lines run from south to north outside a magnet — they run from north to south.
3
Field lines can cross — they never touch or cross.
4
Copper and aluminium are magnetic — only iron, steel, nickel and cobalt are.
Marked practiceQuizzes for this lesson
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