Why is a lightning conductor (arrestor) constructed with sharp copper points installed on the highest point of tall buildings?
💡 UNEB Examiner Insight & Textbook Rationale
A lightning conductor consists of sharp copper spikes on the roof connected to a heavy copper tape leading into moist ground, safely dissipating storm charges into the earth.
P.7 • Topic 2 Question 2 of 8
1 Mark • UNEB Standard
What is the specific role of manganese dioxide ($MnO_2$) in a dry Leclanché cell?
💡 UNEB Examiner Insight & Textbook Rationale
Manganese dioxide acts as a chemical depolarizer in dry cells. It slowly reacts with and oxidizes accumulated hydrogen gas bubbles into harmless water, preventing polarization.
P.7 • Topic 2 Question 3 of 8
1 Mark • UNEB Standard
Why are electrical circuits in modern residential houses wired in parallel rather than in series?
💡 UNEB Examiner Insight & Textbook Rationale
In parallel wiring, each electrical appliance connects across independent branches receiving full line voltage. If one lamp burns out or is switched off, other branch circuits remain active.
P.7 • Topic 2 Question 4 of 8
1 Mark • UNEB Standard
Which of the following non-metallic materials is a good conductor of electricity due to its free electrons?
💡 UNEB Examiner Insight & Textbook Rationale
Graphite is an allotrope of carbon arranged in hexagonal planar layers with delocalized free electrons that can migrate freely, making it an excellent non-metallic electrical conductor.
P.7 • Topic 2 Question 5 of 8
1 Mark • UNEB Standard
How does an electric fuse protect expensive domestic appliances and wiring from fire hazards?
💡 UNEB Examiner Insight & Textbook Rationale
A fuse contains a short piece of thin metal alloy wire with a low melting point. When dangerous surges or short circuits produce excessive current, the wire heats, melts, and opens the circuit.
P.7 • Topic 2 Question 6 of 8
1 Mark • UNEB Standard
In a standard three-pin plug, which wire is connected to the top-most, longest, and thickest pin for safety?
💡 UNEB Examiner Insight & Textbook Rationale
The earth pin is the longest and thickest pin on a 3-pin plug. It connects to the earth wire (green/yellow), earthing the appliance’s metal casing to divert fault currents safely into the ground.
P.7 • Topic 2 Question 7 of 8
1 Mark • UNEB Standard
An electrician measures electric current flowing through a television circuit. Which unit and instrument are utilized?
💡 UNEB Examiner Insight & Textbook Rationale
Electric current (the rate of flow of electric charges) is measured in Amperes (A) using an Ammeter, which must always be connected in series with the load.
P.7 • Topic 2 Question 8 of 8
1 Mark • UNEB Standard
What primary energy transformation occurs in a bicycle dynamo when a cyclist rides at night?
💡 UNEB Examiner Insight & Textbook Rationale
A bicycle dynamo utilizes electromagnetic induction: the spinning wheel provides mechanical kinetic energy to rotate a magnet within copper wire coils, generating electrical current to illuminate the lamp.
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