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9.2Chapter 9: Energy Resources

Generating electricity — Alhussan Physics - Stage 8 Revision Notes & Topical Questions

5 min read 7 parts Lesson 2 of 7 2 quizzes

📚 Alhussan Physics - Stage 8 Hub / Topical Revision
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Lesson summary

Physics 9.2 Generating electricity — Turbines, Generators and Electromagnetic Induction — Alhussan International Academy — Physics (Stages 7–9) notes: Explain electromagnetic induction and describe how simple generators and power station generators work.Voltage needed — To make a…

  • Link with magnetism
  • Induced voltage
  • Movement needed
  • Relative movement
  • Bicycle dynamo
  • Electromagnets

Part 1 of 5What generating electricity means

Voltage needed
  • To make a current flow in a circuit a voltage is needed.
Generating
  • Generating electricity means producing a voltage so that a current is possible.
Link with magnetism
  • A current in a wire produces a magnetic field, and the reverse also happens: a changing magnetic field produces a voltage.

Part 2 of 5Electromagnetic induction

Induced voltage
  • Moving a magnet into a coil connected to a voltmeter produces a voltage in the coil.
Movement needed
  • The voltmeter shows a reading only while the magnet moves.
  • Moving the magnet towards the coil gives a positive reading.
  • Holding the magnet still gives zero.
  • Moving the magnet away gives a negative reading.
Relative movement
  • It does not matter whether the magnet or the coil moves.
Current
  • If the voltmeter is replaced by a lamp or other component, a current flows.
Reversing
  • Reversing the direction of movement, or the poles, reverses the voltage.

Part 3 of 5Increasing the induced voltage

ChangeEffect on induced voltage
Faster movementLarger
Stronger magnetLarger
More turns on the coilLarger
Iron core in the coilLarger
Direction reversedVoltage reversed
No movementZero

Part 4 of 5Simple generators

1Dynamo
  • A simple generator usually has a coil of wire and a magnet that spins when you turn a handle.
  • The spinning magnet keeps changing the field through the coil, so a voltage is induced.
2Bicycle dynamo
  • As you pedal, the wheel moves the dynamo, which powers the lights, so no battery is needed.

Part 5 of 5Generators in power stations

Size
  • Power station generators are very, very big.
Electromagnets
  • They use moving electromagnets instead of permanent magnets because electromagnets produce a much stronger field, giving a bigger induced voltage.
Turbines
  • Turbines spin the generators and may be turned by steam, water or wind.
Energy transfer
  • A generator transfers kinetic energy to electrical energy and is the opposite of a motor.

Key terms

TermMeaning
Induced voltageA voltage produced in a coil when there is relative movement between it and a magnet.
GeneratorA device that transfers kinetic energy to electrical energy.
DynamoA simple generator with a coil and a spinning magnet.
TurbineA wheel turned by steam, water or wind to spin a generator.
Electromagnetic inductionThe production of a voltage by a changing magnetic field.

Avoid these mistakes

1
Thinking a stationary magnet in a coil induces a voltage — there must be relative movement.
2
Thinking only the magnet can move — the coil can move instead.
3
Thinking power stations use permanent magnets — they use electromagnets for a bigger voltage.
4
Thinking generators create energy — they transfer kinetic energy to electrical energy.

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