Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

Unit 9: Magnetism and electromagnets

GRADE 7 – Unit 9: Magnetism and electromagnets — HIA International - Grade 7 Revision Notes & Topical Questions

5 min read 8 parts Lesson 1 of 5 1 quiz

📚 HIA International - Grade 7 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

GRADE 7 - Unit 9: Magnetism and electromagnets — HIA INTERNATIONAL notes: Describe magnets, magnetic fields and the Earth as a magnet, and explain how to make, investigate and use an electromagnet.Magnetic materials — iron, steel, nickel and cobalt are attracted to magnets.Non-ma…

  • Non-magnetic metals
  • Test for a magnet
  • Field lines
  • Detecting a field
  • Two magnets
  • Temporary magnet

Part 1 of 6Magnets and magnetic materials

Magnetic materials
  • Magnetic materials iron, steel, nickel and cobalt are attracted to magnets.
Non-magnetic metals
  • Non-magnetic metals copper, aluminium and zinc are not attracted.
Poles
  • Poles a magnet has a north pole and a south pole; like poles repel and unlike poles attract.
Test for a magnet
  • Test for a magnet only repulsion proves an object is a magnet, because a magnet attracts any magnetic material.

Part 2 of 6Magnetic fields

Magnetic field
Magnetic field the area around a magnet where its effects can be detected.
Field lines
  • Field lines they show the direction of the field, from north to south outside the magnet.
  • The lines never touch or cross.
  • The field is strongest where the lines are closest, at the poles.
Detecting a field
  • Detecting a field use a compass or iron filings, or watch whether a magnetic object is attracted.
Two magnets
  • Two magnets opposite poles give field lines in the same direction and attract;
    • like poles give opposite directions and repel.
1
Place a bar magnet on paper and draw around it.
2
Put a plotting compass near the north pole and mark the needle position.
3
Move the compass so its tail is at the mark and repeat.
4
Join the marks into a smooth line and add an arrow from north to south.

Part 3 of 6The Earth as a giant magnet

Shape
  • Shape the Earth’s field is similar to that of a bar magnet.
Compass
  • Compass the needle points to magnetic north, close to the geographic north pole, which is really a magnetic south pole.
Origin
  • Origin the iron and nickel core, with movement in the liquid outer core, produces the field.
Changes
  • Changes magnetic north moves slowly, about 60 km per year, and the field has reversed in the past.
Uses
  • Uses navigation by ships and aeroplanes, and by some animals such as birds.

Part 4 of 6Making an electromagnet

Electromagnet
  • Electromagnet a coil of insulated wire wrapped around an iron core that becomes a magnet when current flows.
Temporary magnet
  • Temporary magnet it is magnetic only while current flows; switching off drops the paper clips.
Poles
  • Poles found with a compass or a bar magnet, and reversed by reversing the current or the winding.
Making an electromagnet
Wind insulated wire around an iron nail.
Connect the ends to a cell and switch.
Switch on and test with paper clips.

Part 5 of 6Investigating electromagnet strength

Factors
  • Factors more turns on the coil, a larger current and a soft iron core all make an electromagnet stronger.
Measurement
  • Measurement count the paper clips the electromagnet holds.
Independent variable
  • Independent variable the number of turns.
    • (or the current or core material)
Dependent variable
  • Dependent variable the number of paper clips picked up.
Control variables
  • Control variables current, same nail and same clips.
Reliability
  • Reliability repeat readings, calculate means and treat anomalous results with care.
Graphs
  • Graphs use a line graph for turns or current and a bar chart for core material.

Part 6 of 6Uses of electromagnets

Examples
  • Examples scrapyard cranes, electric bells, fire doors, toasters, MRI scanners, relays, loudspeakers and electric motors.
Advantage
  • Advantage an electromagnet can be switched on and off and its strength changed.
Bell
  • Bell the electromagnet pulls the hammer to the gong and the circuit then breaks, so the hammer springs back and the cycle repeats.
Relay
  • Relay a small current in an electromagnet closes a switch in a second circuit.

Key terms

TermMeaning
Magnetic fieldThe area around a magnet where a magnetic material or magnet feels a force.
Field linesLines showing the direction of a magnetic field, from north to south.
Plotting compassA small compass used to trace field lines.
ElectromagnetA coil of wire with a core that is magnetic only while current flows.
Temporary magnetA magnet that is magnetic only while current flows.
Independent variableThe variable you change in an investigation.
Dependent variableThe variable you measure.
Control variableA variable kept the same in a fair test.

Avoid these mistakes

1
Attraction proves something is a magnet — only repulsion does, since a magnet attracts any magnetic material.
2
Copper and aluminium are magnetic — only iron, nickel, cobalt and steel are.
3
Field lines go from south to north outside a magnet — they go north to south.
4
An electromagnet stays magnetic when switched off — it is a temporary magnet.
5
Changing more than one variable in the investigation — change only the turns and keep current, nail and clips the same.

Last updated: