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7.2 Power and efficiency

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Question 33
H

A 1.8 kW kettle takes 3.5 minutes to boil some water.

A 2.8 kW kettle has the same efficiency. It is used to boil the same mass of water from the same starting temperature.

How long does the 2.8 kW kettle take?

[1]
A

135 s135\ \text{s}135 s

B

327 s327\ \text{s}327 s

C

210 s210\ \text{s}210 s

D

2.3 s2.3\ \text{s}2.3 s

Markscheme

7.2 Power and efficiency Questions

  1. GCSE
  2. /Physics
  3. /7.2 Power and efficiency

50 exam-style questions on OCR GCSE Physics 7.2 Power and efficiency, covering 7.2.1 Dissipation of energy, 7.2.2 Energy transfers in domestic devices, 7.2.3 Power ratings of domestic appliances, 7.2.4 Efficiency of energy transfers, 7.2.5 Ways to increase efficiency, 7.2.6 Reducing unwanted energy transfers, and 7.2.7 Thermal conductivity and the cooling of buildings. Each one has a worked solution and a mark scheme showing where the marks go.

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