CAIE IGCSE Physics 4.2.5.4 Kilowatt Hour Kwh and Calculate the Questions

Practise defining the kilowatt-hour, calculating appliance energy from power and time, and multiplying energy in kWh by a tariff to find cost.

Exam points

define one kilowatt-hour as a 1 kW appliance operating for one hour
calculate energy in kWh from kilowatts and operating hours
multiply kWh by price per unit to calculate cost

[Maximum number: 2]

An electric heater uses a resistance wire of resistance $26 \Omega$ . The power dissipated in the resistance wire is 2500 W .

The 2500 W heater is used in a country where electricity costs 0.30 dollars per kilowatt-hour.

Calculate the cost of using the heater continuously for two days.
cost = dollars [2]

(cost =) $36
$E=P t \mathbf{A N D}(\operatorname{cost}=) E \times 0.3(0) \mathbf{O R}(\operatorname{cost}=) 25 \times 10^{N} \times 2 \times 24 \times 0.3(0)$

OR $3.6 \times 10^{\mathrm{N}}$ dollars

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CAIE IGCSE Physics 4.2.5.4 Kilowatt Hour Kwh and Calculate the Questions question 1