P3 General Studies: Home Electricity Safety (Paper 2 (intermediate))

2026-11-13

Tutor Prep Guide · conductors and insulators, power and electricity cost, series and parallel circuits, fuses and earth protection, and safe habits at home

Paper two adds circuits and calculations: series against parallel, earth protection, resistance and shared voltage, cost and fuse choice.

Direct answers　Decide first whether the circuit is series or parallel, then how current and voltage are shared, and only then work out power and cost.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: P3 General Studies: Home Electricity Safety
Level	parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety

02　Questions (10 items)

FoundationOne lamp in a series circuit burns out. What happens to the other lamps?
FoundationWhy are household appliances connected in parallel?
FoundationWhat is the purpose of the earth wire in a three-pin plug?
IntermediateAn appliance runs at 220 V with a current of 0.5 A. What is its resistance in ohms?
IntermediateTwo identical lamps in series are connected to 220 V. What voltage does each lamp get?
IntermediateA 60 W lamp and a 100 W lamp are both on for 4 hours. What is the total energy used in units?
ChallengeA 1500 W appliance runs 3 hours a day for 30 days. How many units does it use and what is the cost at $1.2 per unit?
ChallengeA 1000 W appliance works at 220 V. What current does it take, and is a 5 A fuse suitable?
ChallengeWhy does a short circuit trip the breaker or blow the fuse at once?
Error redoSomeone replaces a blown fuse with a piece of copper wire. Why is this wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	They all go out, because the circuit is broken.	A series circuit has only one path, so one break stops the current everywhere.
2	Each appliance has its own switch, so one failure does not stop the others.	In parallel every branch has the same voltage and can be switched on its own.
3	It carries leakage current safely to the ground and protects the user.	The earth wire is joined to the metal case, so leaking current goes to earth instead of through a person.
4	440.0 ohms	Resistance is voltage divided by current: two hundred twenty divided by zero point five gives 440 ohms.
5	110 V	In series the voltage is shared equally: two hundred twenty divided by two gives 110 V.
6	0.64 units	The total power is 160 W, and one hundred sixty times four gives 640 Wh, which is 0.64 units.
7	135.0 units, $162.0	Fifteen hundred times three times thirty gives 135000 Wh, that is 135 units, and times 1.2 makes 162.0 dollars.
8	4.5 A, so a 5 A fuse is suitable	One thousand divided by two hundred twenty is about 4.5 A, which is below 5 A, so the fuse will not blow.
9	A short circuit has almost no resistance, so the current suddenly becomes very large.	The large current operates the magnetic trip and cuts the circuit.
10	Copper melts at a high temperature, so an overload will not break it and the wiring overheats and catches fire.	The whole point of a fuse is to melt first when the current is too large.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Then try paper three, using voltage and current to work out power and resistance.Tutor Registration →

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