S4.13.6 For the adult
Generators and dynamos
A bicycle lamp lights as you pedal, with no battery. A power station lights a whole city. How do they make electricity?
What this chapter teaches
A generator turns a coil in a magnetic field, or a magnet in a coil, and induces a voltage, changing movement energy into electrical energy. Slip rings make an alternator, with AC. A split ring makes a dynamo, with DC in pulses. One turn of a simple coil is one cycle, so the frequency is the turns each second.
Three questions to ask
There is no one right wording. Listen for the idea.
- How does a generator change movement into electricity?
- What is the difference between the output of an alternator and a dynamo?
- How would you work out the time for one cycle of 50 Hz AC?
After the chapter, the learner can
- Explain how a bicycle dynamo or a power station generator works
- Compare the output of an alternator with that of a dynamo
What they copy into their notebook
A generator turns a coil in a field and induces a voltage. Slip rings: AC (alternator). Split ring: DC pulses (dynamo). One turn is one cycle. Period = 1 ÷ frequency. Faster gives more voltage.