Science 7–10 · Year 9

Generating electricity: a magnet moving through a coil and a hand-cranked generator

Physical sciences — Energy, content group Sources of energy (NSW Stage 5 focus area)

PracticalLow risk

The idea

A generator produces electrical energy only while something keeps a magnet and a coil moving past each other, and the mechanical work done turning it is transformed into the electrical energy the circuit uses; power stations produce electricity the same way, with steam, wind or falling water doing the turning.

What you need

coil of 600 to 1200 turns of insulated wire on a hollow former, 1
bar magnet that fits inside the former, 1
centre-zero galvanometer or a digital multimeter on its 200 mV range, 1
hand-cranked generators (such as a Genecon), 2 (the second for the extension)
6 V 0.06 A lamp in a holder, 1
4 mm leads, 6

How to do it

Before each step, predict what the meter or lamp will show and write the prediction down.
Connect the coil to the galvanometer. Hold the magnet still inside the coil and note the reading (zero).
Push the magnet into the coil and pull it out again while watching the needle; then hold the magnet still and move the coil instead. Record when the needle moves and which way.
Connect the hand generator to the lamp and turn the handle slowly, then quickly; note the brightness.
Turn the handle at a steady rate with the lamp connected and then disconnected, and compare how hard the handle is to turn.
Extension: connect the generator to a second generator and turn one; observe the other's handle.
Use the observations to explain where the lamp's energy comes from, and how a power station's turbine and generator produce electricity from steam, wind or falling water.

What you should see

No reading while the magnet is still. Pushing the magnet in moves the needle one way and pulling it out moves it the other way; the needle returns to zero whenever the motion stops, and moving the coil instead of the magnet gives the same pattern. The hand generator lights the lamp only while it is turning, brighter when faster, and the handle becomes noticeably harder to turn when the lamp is connected: the mechanical work done on the handle supplies the lamp's energy, so the generator transforms energy rather than making it. In the extension, turning one generator's handle turns the other's.

What changes

What you change: whether the magnet or coil is moving, and whether the lamp is connected to the generator
What you measure: galvanometer deflection, lamp brightness and how hard the handle is to turn
What you keep the same: same coil and magnet
same meter range
same generator and lamp

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A magnet sitting in a coil produces a steady current.
A generator makes energy from nothing.
Electricity comes from the wall, not from a generator somewhere.

Safety card

Low riskLearners carry it out

Hazards

fingers caught in the generator crank
strong magnets pinching

Controls

hold the generator body, not the gears
keep magnets away from phones and cards

Note

No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC5-EGY-01 SC5-WS-01 SC5-WS-02 SC5-WS-06
Australian Curriculum v9AC9S9U05AC9S9I01AC9S9I05

Sources

The pages the author read to write this activity.

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