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Electrical Safety

Basic Science & Engineering · Heat, Electricity & Technical Basics

Overview

Electrical safety prevents shocks and fires through earthing, protective devices, correct wiring and safe working practice.

Key points

Earthing provides a safe path for leakage current.
A fuse or MCB breaks the circuit on overload or short circuit.
An RCCB/ELCB trips on earth leakage and protects people from shock.
Current wiring colours: brown (live), blue (neutral), green-yellow (earth); older wiring: red, black, green.
Never use water on an electrical fire; use CO₂ or dry chemical powder.

Explanation

First aid for shock: switch off the supply first or separate the person with a dry non-conducting object.
Work on circuits only after isolation and lock-out/tag-out.
Do not touch switches with wet hands.
Use insulated tools and rubber mats.

Step by step

Identify the concept, tool or rule involved.
Recall the definition, value or procedure.
Check units, safety logic and the direction of the effect.

Examples

The device that protects people from earth-leakage shock → RCCB/ELCB.
The correct extinguisher for an electrical fire → CO₂ or dry chemical powder.
First step for a shock victim → switch off the supply or separate with a dry insulator.

Traps and advanced points

Trap: Using water on electrical fires.
Trap: Touching the victim directly.
Trap: Thinking a fuse protects people from shock.

Quick revision

Earth, fuse/MCB, RCCB.
No water on electrical fires.
Isolate before work.

Practice MCQs

ALP Basic Science & Engineering: Which statement opening is correctly completed by “direction”?
1. an isometric drawing is mainly used to
2. a strong password is improved by
3. power is measured in
4. velocity differs from speed because velocity includes
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Answer: (d) velocity differs from speed because velocity includes. Velocity is a vector; speed is scalar.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “small lengths/diameters with finer precision”?
1. vernier caliper is commonly used to measure
2. first-angle and third-angle projection are methods used in
3. an isometric drawing is mainly used to
4. for an electrical fire, water is generally
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Answer: (a) vernier caliper is commonly used to measure. It offers finer reading than an ordinary scale.
A concave lens is commonly used to correct which defect?
1. Hypermetropia
2. Colour blindness
3. Myopia
4. Presbyopia only
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Answer: (c) Myopia. A concave lens is commonly used to correct Myopia.
Frequency is measured in which unit?
1. hertz
2. tesla
3. decibel
4. newton
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Answer: (a) hertz. Frequency is measured in hertz.
Ohm’s law relates voltage, current and what?
1. Temperature only
2. Mass
3. Resistance
4. Pressure
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Answer: (c) Resistance. Ohm’s law relates voltage, current and Resistance.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “protect a circuit from excessive current”?
1. vernier caliper is commonly used to measure
2. a fuse is primarily used to
3. first aid for severe electrical shock begins with
4. velocity differs from speed because velocity includes
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Answer: (b) a fuse is primarily used to. Fuse element melts when current exceeds safe value.
ALP Basic Science & Engineering: Complete the statement: “A fuse is primarily used to ____.”
1. R₁ + R₂
2. protect a circuit from excessive current
3. very small thickness or diameter
4. engineering drawing
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Answer: (b) protect a circuit from excessive current. Fuse element melts when current exceeds safe value.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “a low-resistance path for fault current”?
1. earthing primarily provides
2. a strong password is improved by
3. electrical power in a DC circuit can be written as
4. an operating system mainly
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Answer: (a) earthing primarily provides. It reduces shock risk when exposed metal becomes live.
ALP Basic Science & Engineering: Complete the statement: “Earthing primarily provides ____.”
1. a low-resistance path for fault current
2. greenhouse gases
3. joule
4. load/effort
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Answer: (a) a low-resistance path for fault current. It reduces shock risk when exposed metal becomes live.
ALP Basic Science & Engineering: Complete the statement: “For an electrical fire, water is generally ____.”
1. unsafe on live electrical equipment
2. a low-resistance path for fault current
3. watt
4. metre
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Answer: (a) unsafe on live electrical equipment. For an electrical fire, water is generally unsafe on live electrical equipment. Isolate supply and use an appropriate extinguisher.