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Electrical Engineering › Installation, Earthing & Safety

Protective Devices (MCB, RCCB, ELCB) MCQ [Free PDF] – 4 Objective Questions with Answers

Every Protective Devices (MCB, RCCB, ELCB) question asked in GPSC DEE Electrical, GPSC AE Electrical, Supervisor Instructor — solve, check instantly, then read the formula and exam tip.

4 PYQs4 subtopics3 examsUpdated 23 Oct 2026
Topic practice0/4✓ 0✗ 0

ELCB and RCCB (1)

Q1Easy
Asked in: GPSC DEE Electrical · DEE Master paper · 2026
Consider the following regarding Earth Leakage Protection:
1. An ELCB (Earth Leakage Circuit Breaker) detects small leakage currents to the earth.
2. Voltage-operated ELCBs are preferred over current-operated RCCBs in modern installations.
3. A 30mA RCCB is generally used for personal protection against electric shock.
Which of the statements given above is/are correct?
View answer & solution
Correct answer: B. 1 and 3 only
Quick explanation

An RCCB/RCD detects imbalance between live and neutral currents caused by leakage to earth and is used for shock protection. An MCB protects conductors against overload and short circuit. Key relation: Typical additional personal protection uses 30 mA RCD/RCCB.

Exam focus: RCCB → leakage; MCB → overcurrent; SPD → transient surge. Common trap: Do not expect an RCCB alone to provide overload protection.

Verified · SRO editorial deskSolution page → Report

Kit-Kat Fuse (1)

RCCB MCB and SPD (1)

Q3Easy
Asked in: GPSC DEE Electrical · DEE Master paper · 2026
Regarding electrical safety and protection devices:
1. An RCCB (Residual Current Circuit Breaker) protects against earth leakage currents,which helps prevent electric shocks.
2. An MCB (Miniature Circuit Breaker) provides protection against both overload and short-circuit faults.
3. Surge Protection Devices (SPDs) are designed to handle sustained overvoltage conditions.
Which of the statements given above is/are correct?
View answer & solution
Correct answer: A. 1 and 2 only
Quick explanation

An RCCB/RCD detects imbalance between live and neutral currents caused by leakage to earth and is used for shock protection. An MCB protects conductors against overload and short circuit. Key relation: Typical additional personal protection uses 30 mA RCD/RCCB.

Exam focus: RCCB → leakage; MCB → overcurrent; SPD → transient surge. Common trap: Do not expect an RCCB alone to provide overload protection.

Verified · SRO editorial deskSolution page → Report

Residual Current Protection (1)

Q4Easy
Asked in: GPSC AE Electrical · AE R&B · 2025 · Series M
What is the primary function of an RCCB (Residual Current Circuit Breaker) in an electrical system?
View answer & solution
Correct answer: D. To protect humans from electric shock due to earth faults
Quick explanation

An RCCB protects people against dangerous earth-leakage/residual current by comparing the currents in live and neutral conductors. If the imbalance exceeds its trip threshold, it disconnects the circuit rapidly.

I_Δ = |IL − IN| If I_Δ ≥ trip threshold → RCCB trips
Verified · SRO editorial deskSolution page → Report
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