PHYSICS · Stage 8 · Chapter 9: Energy Resources
Physics 9.2 Generating electricity — Turbines, Generators and Electromagnetic Induction
5 min read 5 parts Lesson 2 of 7
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
Section 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.
Section 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.
Section 3 of 5Increasing the induced voltage
| Change | Effect on induced voltage |
|---|---|
| Faster movement | Larger |
| Stronger magnet | Larger |
| More turns on the coil | Larger |
| Iron core in the coil | Larger |
| Direction reversed | Voltage reversed |
| No movement | Zero |
Section 4 of 5Simple generators
- Dynamo
- 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.
- Bicycle dynamo
- As you pedal, the wheel moves the dynamo, which powers the lights, so no battery is needed.
Section 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.
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