Electrostatics — KCSE Physics

KCSE Physics · 114 practice questions · 6 syllabus objectives

38 easy39 medium37 hard

What You'll Learn

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

State that objects can be charged by friction, induction and contact; describe the gold leaf electroscope

Apply Coulomb’s law (F = kq₁q₂/r²) to calculate the electrostatic force between point charges

Describe and draw electric field patterns around point charges and between parallel plates

Explain charge distribution on conductors, action at points, lightning and lightning conductors

Define capacitance; calculate effective capacitance in series and parallel; solve problems involving Q = CV and E = ½CV²

Electrostatics

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easySHORT ANSWER3 marks

State how a lightning conductor protects a building from lightning strikes by explaining the role of charge distribution. (3 marks)

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Part (a) — 3 marks

The lightning conductor provides a direct path to the ground for the electrical charge from the lightning. (1 mk)

It allows excess charge to flow safely away from the building, preventing damage. (1 mk)

The presence of the conductor alters the electric field around the building, reducing the likelihood of a strike. (1 mk)

easySHORT ANSWER3 marks

Identify the characteristics of the electric field around a single positive point charge. (3 marks)

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Part (a) — 3 marks

The electric field lines radiate outward from the charge (1 mk)

Field lines are perpendicular to the surface of the charge (1 mk)

The density of field lines indicates the strength of the electric field (closer lines = stronger field) (1 mk)

easySHORT ANSWER3 marks

Two point charges, +3 μC and -2 μC, are placed 0.5 m apart in a vacuum. Calculate the electrostatic force between them using Coulomb's law. (3 marks)

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Part (a) — 3 marks

Identify the values: q₁ = 3 μC, q₂ = -2 μC, r = 0.5 m (1 mk)

Use Coulomb's law: F = k * |q₁ * q₂| / r² (where k = 8.99 x 10⁹ N m²/C²) (1 mk)

Calculate the force: F = (8.99 x 10⁹) * (3 x 10⁻⁶ * 2 x 10⁻⁶) / (0.5)² = 0.2154 N (1 mk)

Describe the function of a gold leaf electroscope in detecting electric charge. (4 marks)

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