3-ELE-07

Outcomes

• Pupils can
• Use of P = IV, higher currents leads to hotter wires
• Ammeter in series, voltmeter in parallel

Specification References

2.6 recall and use the relationship, power = current x voltage, P=IV and apply the relationship to the selection of appropriate fuses

Starter

Reminder from previous lesson that Power = IV. A couple of calculations done in there rough books to get students using the equation again and to check any who are struggling with this. Light bulbs have power ratings eg 100W, 40W. What does this mean?

Question: Does a 100W bulb always give out power of 100W?

Main Body of Lesson

• Use of different fuse wires to discover the heating effect of a wire depends on current, thin wires heat up more for same current

Plenary

• Thin wires heat up more – use of this idea to break a circuit
• Use – fuses
• Dangers of fire when using the wrong flex in low current appliances

Homework

Worksheet: Practice using P=IV and choosing fuse values

Additional Information

Resources Required

• Various fuse wires, heat proof mats, high current variable dc supplies, ammeters, voltmeters, 2.5V bulbs.
• P=IV and fuse value practice sheet

Skills Addressed

Practical skills – building circuits

Safety/Hazards

• Burns – students must not touch wires and should be told what to do if they recieve a burn.

Electricity Outline

Electricity