Mains electricity — KCSE Physics

KCSE Physics · 70 practice questions · 4 syllabus objectives

24 easy23 medium23 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

State sources of mains electricity and describe power transmission from generation to consumer

Explain the domestic wiring system including live, neutral, earth wires and fuses

Define the kilowatt hour, determine electrical energy consumption and cost

Select appropriate fuses, calculate current and power for mains appliances

Sample Questions

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1
easySHORT ANSWER3 marks

List three factors that determine the appropriate fuse rating for an electrical appliance. (3 marks)

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Part (a) — 3 marks
The power rating of the appliance in watts (1 mk)
The voltage supply of the circuit (1 mk)
The type of appliance and its usage patterns (1 mk)
2
easySHORT ANSWER2 marks

State two factors that determine the cost of electricity consumed in a household. (2 marks)

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Part (a) — 2 marks
The total energy consumed in kilowatt hours (kWh). (1 mk)
The cost per kilowatt hour charged by the electricity provider. (1 mk)
3
easySHORT ANSWER3 marks

State the definition of a kilowatt hour and how it relates to electrical energy consumption. (3 marks)

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Part (a) — 1 mark
A kilowatt hour is the amount of energy consumed by a device of one kilowatt running for one hour. (1 mk)
Part (b) — 2 marks
It quantifies electrical energy consumption in households and industries. (1 mk)
It is used to calculate electricity bills by multiplying energy consumed in kWh by the unit cost. (1 mk)
4

State the colour coding of the three main wires used in domestic electricity and explain the role of a fuse in the system. (4 marks)

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