WAEC 2025 Basic Electricity Questions & Answers

WAEC 2025 Basic Electricity Questions & Answers

BASIC ELECTRICITYj

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41-50: DBCBCDCADB

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WAEC BASIC ELECTRICITY

(2a)
Impedance (Z) is the total opposition to the flow of alternating current (AC) in a circuit, which combines both resistance (R) and reactance (X).

(2b)
(Draw the diagram)

(2ci)
Given:
Output RMS Voltage Vrms = 220V
Maximum voltage (Vmax) = Vrms x (√2)
Vmax = 220 x (√2)
Vmax = 220 x 1.414
Vmax = 310.88V

(2cii)
Average value (Vavg) = (2/π) x Vmax
Vavg = (2/π) x 310.88
Vavg = 0.636 x 310.88
Vavg = 197.25V

(5a)
Draw the diagram

(5b)
(PICK ANY ONE)
(i) Voltage Step-Up: Increases voltage at the generation end for efficient long-distance transmission (reduces current and power losses).
(ii) Voltage Step-Down: Decreases voltage at the distribution end to safe levels suitable for homes and industries.
(iii) Impedance Matching: Helps in matching impedance between components for maximum power transfer and system efficiency.
(iv) Electrical Isolation: Provides isolation between different parts of the system to enhance safety and system protection.

(6a)
Lightning Arrester:
(i) Diverts lightning surges to earth.
(ii) Protects transformers from high voltage.
(iii) Prevents damage to substation equipment.
(iv) Limits transient overvoltages.
(v) Ensures safety during lightning storms.

(6b)
Circuit Breaker:
(i) Interrupts current during faults.
(ii) Operates automatically or manually.
(iii) Protects equipment from overload.
(iv) Isolates faulted sections.
(v) Ensures system stability.

(6c)
Isolator:
(i) Disconnects parts of the system.
(ii) Used during maintenance.
(iii) Operates only under no load.
(iv) Provides visible isolation.
(v) Enhances safety for workers.

(7ai)
(i) Reduces equipment failure: Regular maintenance helps identify and fix potential problems before they cause breakdowns.
(ii) Extends equipment lifespan: Preventive care ensures devices operate efficiently for a longer time.

(7aii)
(i) Worn-out or faulty capacitor, which can prevent the fan from starting or running at proper speed.
(ii) Damaged or loose wiring, which may lead to malfunction or electrical hazards.

(7bi)
Possible Cause of the Fault:
The possible cause is a short circuit or insulation failure in the kettle, causing the metal body to become energized.

(7bii)
Corrective Action:
Disconnect the kettle from power immediately and have it inspected and repaired or replaced by a qualified electrician.

(7biii)
Preventive Measure:
Regular inspection and maintenance of electrical appliances, including checking for worn-out insulation, damaged cords, or faulty grounding, can prevent such faults.

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