Heating effect of electric current — KCSE Physics

KCSE Physics · 108 practice questions · 4 syllabus objectives

30 easy39 medium39 hard

What You'll Learn

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

Perform experiments to illustrate heating effect and state factors affecting it

Derive the equations for electrical energy E = VIt and electrical power P = VI

Identify heating devices and solve numerical problems involving electrical energy, power, and cost

Select appropriate fuses for circuits and explain safety features of heating elements

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easySHORT ANSWER4 marks

State the units of electrical energy and electrical power. (4 marks)

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Part (a) — 1 mark

The unit of electrical energy is the joule (J) (1 mk)

Part (b) — 1 mark

The unit of electrical power is the watt (W) (1 mk)

Part (c) — 1 mark

The joule represents the amount of energy transferred when one coulomb of charge moves through an electric potential of one volt (1 mk)

Part (d) — 1 mark

The watt represents the rate of energy transfer equivalent to one joule per second (1 mk)

easySHORT ANSWER3 marks

Explain how electrical power can be calculated using voltage and current. (3 marks)

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Part (a) — 3 marks

Electrical power is given by the equation P = VI (1 mk)

Where P represents power, V is voltage, and I is current (1 mk)

Power indicates the rate at which electrical energy is consumed or converted (1 mk)

easySHORT ANSWER2 marks

Identify the equation that relates electrical energy to voltage, current, and time. (2 marks)

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Part (a) — 2 marks

E = VIt (1 mk)

Where E is electrical energy, V is voltage, I is current, and t is time (1 mk)

Identify two factors that determine the rating of a fuse used in an electric circuit and explain their significance. (4 marks)

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