4-ELM-01

Outcomes

• pupils know what a electromagnet is and how you can build one
• students can state four ways of increasing the power of an electromagnet
• students explain how the electric bell and different relays work

Specification References

• 6.9 describe construction of electromagnets

Starter

• Using the mini white boards ask pupils to recall the shape of a magnetic field around a bar magnet. Identify the important aspects: continuous filed lines and arrows for direction.
• Show to the pupils a wire wrapped around along nail, connected to a power supply. Ask them what will happen when the power supply will be switched on. Ask them to name the ‘device’. Discuss where and how this ‘device’ could be used.

Main Body of Lesson

• Use the 3 demos of a straight wire, 4 turns and 12 turns to explain how an electromagnet is made and works:
  • a magnetic field will be present around the wire when current is sent through it; the electromagnet is ON.
  • When current is switched off, the electromagnet is OFF.
  • Any piece of iron, nickel or cobalt brought close to this field will be attracted by it.
• Show pupils the electric bell and the relay and discuss how they work.
• Demonstrate the magnetic domains underneath a microscope and the effect of increasing the current.

Plenary

• Use the 'Electric Bell' and 'Relays' worksheet. Pupils should stick them in their books and use them to fully explain how they work.

Homework

• Complete Physics texbook - page 209, Q 1-4

Additional Information

Resources Required

• electric bell demo, different relay demos, circuit breakers RCD's, coils, power supplies, plotting compasses.

Textbook References

• None

Website References

• None

Safety/Hazards

• With high currents the wires may get hot.

Notes

• None