Edexcel IGCSE Physics 2.4 Power, current & voltage

Practise using P = IV to calculate appliance power, compare component brightness and choose electrical ratings with correct units.

Exam points

calculate power from P = IV and convert answers between W and kW
use current and voltage values to decide which lamp or appliance has the greatest power
state or rearrange P = IV, keeping current, voltage and power symbols distinct

[Maximum number: 3]

The diagram shows a domestic lighting circuit.

Figure for Question 2.4 Power, current and voltage 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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2.4 Power, current and voltage question 1