Question

According to the international convention of color coding in a wire
A. Live is red, neutral is yellow, and earth is green
B. Live is red, neutral is green, and the earth is black
C. Live is brown, neutral is blue, and the earth is green
D. Live is red, neutral is black, and the earth is green

Answer 1

Wire color coding is used most probably for wiring houses, commercial industries, industrial panel boards, ect. The electrical color wiring codes are different everywhere in the world according to their standards. For example, in India, red, yellow, and blue, but in Canada, it's red, black, and blue in three-phase. Different colour coding is present for A.C. and D.C. wires.

Complete step by step answer:
The international standard defines the color codes as below:

For a three-phase A.C. system,
The preferred wiring color code for three-phase four-wire systems is as follows:
Phase – 1: Brown
Phase – 2: Black
Phase – 3: Grey
Neutral: Light blue
Earth or protective conductor: Green/Yellow

For a Single-phase AC system,
The preferred wiring color codes for single-phase four-wire systems are as follows:
Phase: Brown
Neutral: Light blue
Earth or protective conductor: Green/Yellow

Wire Unearthed DC system:
Positive: Brown
Negative: Grey
In the above convention, the word phase means relative variation and change of state. Phase in physics also refers to a sinusoidal voltage of A.C supply shift between its positive and its negative. An A.C. system in which all voltages vary at the same sinusoidal pattern is called a single-phase A.C. system, and the three supply phase system consists of three sinusoidal patterns, which are 120 degrees out of phase to each other.

Therefore the correct option is (C).

Note: No power station generates and transmits single-phase power. The power generated at the power stations is always three-phase. But single-phase power can be generated separately using single-phase alternators or converters.