Difference between revisions of "3-ELE-07"
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==[[Specifications|Specification]] References== | ==[[Specifications|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 | + | * 2.6 recall and use the relationship, power = current x voltage, P=IV and apply the relationship to the selection of appropriate fuses |
==Starter== | ==Starter== |
Revision as of 13:12, 16 February 2010
Contents
This lesson will be made part of another lesson. Please continue onto 3-ELE-08.
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
Textbook References
Website References
Skills Addressed
Practical skills – building circuits
Safety/Hazards
Burns – students must not touch wires