Edexcel IGCSE Physics 2.4 Power Current and Voltage Questions

Power depends on current and voltage. Use the equation to check appliances and lamps, then match the operating current with an appropriate fuse.

Exam points

Calculate appliance power using P = IV and give the result in watts or kilowatts.
Rearrange P = IV to calculate operating current from power and voltage, then choose a suitable fuse rating for the appliance.
State and use P = IV, identifying power (P), current (I) and voltage (V) with their correct units.

[Maximum number: 3]

The diagram shows a domestic lighting circuit.

Figure for Question Edexcel IGCSE Physics 2.4 Power Current and Voltage Questions question 1 — Edexcel IGCSE Physics

When switch 1 is closed, the current in lamp 1 is 22 mA .

Show that lamp 1 has a power of about 5 W .

Marking points:
- substitution into formula
- conversion from $\mathrm{mA}$ to $\mathrm{A}$
- evaluation to 2 or more significant figures

Example:
$P=230\times22\times10^{-3}$ $P=230\times0.022$ $P=5.1\ \mathrm{W}$

Accept:
- $5.06\ \mathrm{W}$
- 0.022 or $\div1000$ seen anywhere in working

Ignore:
- units

Marking guidance:
- Condone a calculation of current or voltage given to at least 3 significant figures using a power of $5\ \mathrm{W}$ for full marks.

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Edexcel IGCSE Physics 2.4 Power Current and Voltage Questions question 1