NABTEB Electrical Installation
Past Questions

18+ verified Electrical Installation past questions for NABTEB. Step-by-step worked answers in 5 Nigerian languages.

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Electrical Installation topics (3)

Wiring
1 questions
Safety
1 questions
Tools
0 questions

Sample Electrical Installation past questions

1. SI unit of electric current.

  • A. Volt
  • B. Ohm
  • C. Ampere
  • D. Watt

Answer: C

2. A device that converts electrical to mechanical energy.

  • A. Generator
  • B. Motor
  • C. Transformer
  • D. Battery

Answer: B

3. The unit of electrical resistance is the:

  • A. Volt
  • B. Ampere
  • C. Ohm
  • D. Watt

Answer: C

4. A fuse protects a circuit from:

  • A. Low voltage
  • B. Excess current
  • C. Darkness
  • D. Noise

Answer: B

5. AC stands for:

  • A. Alternating Current
  • B. Active Cable
  • C. Automatic Circuit
  • D. Applied Charge

Answer: A

6. Live, neutral and ___ are the three wires in a plug.

  • A. Earth
  • B. Water
  • C. Gas
  • D. Steel

Answer: A

AI Explanation

**The reasoning** In electrical wiring, every plug has **three essential wires** for safety and proper function: 1. **Live wire** (brown) — carries current TO the appliance 2. **Neutral wire** (blue) — completes the circuit, carrying current AWAY 3. **Earth wire** (green/yellow stripes) — the safety wire that protects you The **earth wire** connects the metal casing of appliances to the ground. If there's a fault and the live wire touches the metal body, the earth wire provides a safe path for the dangerous current to flow into the ground instead of through YOUR body. This trips the fuse/circuit breaker and cuts off power immediately. **Why the wrong options tempt you** - **Water, Gas, Steel** — These aren't electrical components. The question might confuse you if you're thinking about general utilities in a house (water pipes, gas lines) rather than focusing specifically on *electrical* safety systems. **Quick takeaway** Think **L-N-E**: Live brings power in, Neutral takes it out, Earth keeps you safe from shocks — it's your electrical bodyguard.

7. Power (watts) = voltage ×

  • A. resistance
  • B. current
  • C. time
  • D. charge

Answer: B

8. Ohm's law: V =

  • A. I/R
  • B. IR
  • C. I + R
  • D. I × P

Answer: B

AI Explanation

V (volts) = I (amps) × R (ohms).

9. Unit of electric current:

  • A. volt
  • B. ampere
  • C. ohm
  • D. watt

Answer: B

AI Explanation

Current is measured in amperes (A).

10. A circuit breaker:

  • A. increases voltage
  • B. protects circuits by interrupting current during overload/short-circuit
  • C. stores power
  • D. measures current

Answer: B

AI Explanation

Circuit breakers trip to break the circuit when current exceeds safe levels.

11. Earthing (grounding) is used to:

  • A. increase voltage
  • B. provide a safe path for fault current to ground
  • C. reduce light
  • D. lower cost

Answer: B

AI Explanation

Earthing protects users by giving fault current a low-resistance path to ground.

12. A 'fuse' is a:

  • A. voltage booster
  • B. protective device that melts to break a circuit during overcurrent
  • C. lamp
  • D. switch

Answer: B

AI Explanation

Fuses contain a thin wire that melts under excessive current, interrupting the circuit.

13. Power (P) =

  • A. V/I
  • B. I/R
  • C. VI
  • D. R × V

Answer: C

AI Explanation

P = VI (in watts, for resistive loads).

14. Resistors are connected in series:

  • A. resistances add
  • B. resistances are in parallel formula
  • C. resistance becomes zero
  • D. resistance becomes infinite

Answer: A

AI Explanation

In series: R_total = R1 + R2 + R3...

15. An insulator:

  • A. conducts current well
  • B. resists the flow of electric current
  • C. is always made of copper
  • D. stores charge only

Answer: B

AI Explanation

Insulators (rubber, plastic, glass) prevent or limit current flow.

16. Copper is widely used in wiring because it is a good:

  • A. insulator
  • B. conductor of electricity
  • C. magnet
  • D. heat sink only

Answer: B

AI Explanation

Copper has very low electrical resistance — excellent conductor.

17. An electric motor converts:

  • A. heat to light
  • B. electrical energy to mechanical energy
  • C. sound to light
  • D. chemical to heat

Answer: B

AI Explanation

Motors convert electrical to mechanical (rotational) energy. Generators do the reverse.

18. Voltage in a domestic socket in Nigeria is typically:

  • A. 12 V
  • B. 110 V
  • C. 220–240 V
  • D. 440 V

Answer: C

AI Explanation

Nigerian mains supply is approximately 220–240 V AC, 50 Hz.

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