Electric and magnetic forces: electromagnets, motors and generators
Answers are for parents and teachers.
1
Name three uses of electromagnets.
For example, scrap-yard cranes, sorting metals for recycling and electric bells.
2
An electromagnet with 15 turns lifts 4 clips. With twice as many turns, would you expect more or fewer? Why?
More: more turns make a stronger magnetic field (the exact number must be measured).
3
Why does a motor not turn all the energy into movement?
Some energy becomes heat in the coil and the moving parts.
4
A motor takes 30 J and gives 24 J. How much energy becomes heat?
30 J − 24 J = 6 J.
5
Explain in two sentences how a power station turns the movement of steam or water into electrical energy.
The moving water or steam turns a turbine. The turbine turns a generator, in which a coil turns in a magnetic field and produces an emf.