State whether the following statements are true of false:(a) A wire with a green insulation is usually the live wire.
(b) A miniature circuit breaker (MCB) works on the heating effect of current.
(a) False
Explanation
The electric power line enters our house through three wires- namely the live wire, the neutral wire and the earth wire. The first two carry electric current from the power station and the third is earthed by connecting it to the earth through a metal wire called 'Earth Wire'.
To avoid confusion between these three wires, we follow different colour code to insulate these wires. This colour coding of wires helps us to connect the switches, plugs and other electrical components through the appropriate wire in the home wiring circuit.
In old convention, the red wire is the live wire, the black wire is neutral and the earth wire is given green insulation.
In new convention, the brown wire is the live wire, the light blue wire is neutral and the earth wire is given green-yellow insulation.
(b) False
Explanation
A "Miniature Circuit Breaker" (MCB) works on the magnetic effect of current.
In MCB, the incoming terminal is connected via a solenoid coil followed by a bimetallic strip, and the output of the bimetallic strip is connected to the output screw terminal. All the parts are connected in series with each other. Under Normal condition MCB act as a switch. We can turn on or turn off the MCB by using actuator knob.
Under the short circuit and overload condition, the high current flows through the solenoid coil which creates a strong magnetic field, due to which the plunger inside the tripping mechanism gets attracted. The plunger pushes the tripping rod, and the tripping rod trips the circuit breaker without time delay.
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