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Question

What is the color of neutral in three core flexible cables?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

Blue

Understanding Electrical Cable Color Coding

Electrical cables use specific color codes to identify the function of each wire within the cable. This is crucial for safety during installation, maintenance, and repair work, ensuring that wires are connected correctly.

Color of Neutral Wire in Three-Core Flexible Cables

Flexible cables are commonly used for connecting appliances to power outlets. A three-core flexible cable contains three distinct wires, typically serving as the Live, Neutral, and Earth connections.

According to international standards, including the harmonized European standard often followed in many regions, the color coding for a three-core flexible cable is standardized to ensure consistency and safety.

Standard Color Coding for Three-Core Flexible Cables

The standard colors for the conductors in a three-core flexible cable are:

  • Live Wire: Brown
  • Neutral Wire: Blue
  • Earth Wire: Green and Yellow (or Green/Yellow)

Therefore, the color specifically assigned to the neutral wire in a three-core flexible cable is Blue.

Let's look at the role of each wire:

  • Live (Brown): This wire carries the electrical current from the power source to the appliance.
  • Neutral (Blue): This wire completes the circuit, providing a return path for the current back to the power source. Under normal conditions, the potential difference between Neutral and Earth is close to zero.
  • Earth (Green/Yellow): This is a safety wire. It provides a path for fault current to flow safely to the ground in case of an electrical fault, preventing electric shock.

Summary Table of Three-Core Flexible Cable Colors

Wire Function Standard Color (Three-Core Flexible Cable)
Live Brown
Neutral Blue
Earth Green/Yellow

Based on this standard color coding, the color of the neutral wire in three-core flexible cables is Blue.

Revision Table: Electrical Cable Color Codes

Reviewing standard color codes for different cable types is essential for electrical safety.

Wire Function Standard Color (Three-Core Flexible) Standard Color (Fixed Wiring Single Phase)
Live Brown Brown
Neutral Blue Blue
Earth Green/Yellow Green/Yellow

Note that for fixed wiring installations (like wiring within walls), older standards might have used different colors (e.g., Red for Live, Black for Neutral), but the harmonized colors (Brown for Live, Blue for Neutral) are now standard for new installations in many countries, aligning with flexible cable color codes.

Additional Information: Why Color Coding Matters

Correct electrical cable color coding is not just a convention; it's a critical safety measure. Misidentifying wires can lead to:

  • Electric shock hazards.
  • Damage to appliances or electrical systems.
  • Incorrect wiring that prevents circuits from functioning properly.

Always consult local wiring regulations, as specific requirements might vary slightly by region, although the Blue for Neutral and Brown for Live in flexible cables is widely adopted.

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