Ohm's law — KCSE Physics

KCSE Physics · 107 practice questions · 9 syllabus objectives

32 easy38 medium37 hard

What You'll Learn

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

Define EMF, distinguish it from terminal voltage, calculate internal resistance, and solve Wheatstone bridge problems

State Ohm's law and write the formula V = IR; identify ohmic and non-ohmic conductors

Calculate current, voltage or resistance using V = IR and electrical power using P = IV = I²R = V²/R

Plot and interpret an I-V graph; determine resistance from the gradient; identify non-linear behaviour

State Ohm’s law, define resistance, and distinguish between ohmic and non-ohmic conductors

State factors affecting resistance, explain the effect of temperature, and solve resistivity problems

Draw circuit diagrams, describe experiments to verify Ohm’s law, and analyse V-I graphs

Calculate effective resistance for series and parallel combinations and solve circuit problems for current, voltage and power

Ohm's law

Sample Questions

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1
easySHORT ANSWER4 marks

A circuit consists of a 12 V battery connected in series with two resistors, R1 = 4 Ω and R2 = 6 Ω. (a) Calculate the total resistance of the circuit. (2 marks) (b) Determine the current flowing through the circuit. (2 marks)

View Marking Scheme
Part (a) — 2 marks
Total resistance in series, R_total = R1 + R2 = 4 Ω + 6 Ω (1 mk)
R_total = 10 Ω (1 mk)
Part (b) — 2 marks
Using Ohm's law, I = V/R_total = 12 V / 10 Ω (1 mk)
I = 1.2 A (1 mk)
2
easySHORT ANSWER2 marks

Name two factors that determine whether a material obeys Ohm's law. (2 marks)

View Marking Scheme
Part (a) — 2 marks
Temperature of the material must remain constant (1 mk)
Material must have a constant resistivity under the conditions applied (1 mk)
3
easySHORT ANSWER4 marks

A circuit contains a 12 V battery connected in series with two resistors of 4 Ω and 6 Ω. (a) Calculate the total resistance in the circuit. (2 marks) (b) Determine the current flowing through the circuit. (2 marks)

View Marking Scheme
Part (a) — 2 marks
Total resistance, R_total = R1 + R2 = 4 Ω + 6 Ω (1 mk)
Total resistance, R_total = 10 Ω (1 mk)
Part (b) — 2 marks
Current, I = V/R_total = 12 V / 10 Ω (1 mk)
Current, I = 1.2 A (1 mk)
4

List three factors that affect the resistance of a conductor. (3 marks)

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