Question

Which of the following is the function of MCB in house hold circuit ?
(A) This switches automatically turn off where current exceeds safe limit
(B) This switches automatically turn on where current exceeds safe limit
(C) Saves the electrical appliances from getting damage due to excess current
(D) Saves from short circuiting

Answer 1

Hint: Miniature Circuit Breaker (MCB) is an automatic switch which is used as a precautionary measure in case of an overload . As we know that if the circuit is broken then no current flows in the household circuit.

Complete step by step answer:
A MCB is an electro mechanical switch that is automatically operated by action of interrupting the continuity of electrical flow through the circuit once a fault is detected.
In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit
So option (A) is correct.
In case of an excess current, the strip in the MCB is heated and bends. Due to this deflection the latch of the circuit moves leading to opening of the circuit.
When the circuit is open, the excess current does not pass through the electrical appliances leading to their safety.
So option (C) is correct.
When the current passes through an unintended path having very low impedance, the circuit gets damaged leading to overheating or explosion. This is known as Short Circuiting.
This can be prevented by the MCB as the circuit breaks which does not allow the excess current to flow through the circuit.
Hence option (D) is also correct.

So, the correct answer is “Option A,C,D”.

Additional Information:
MCB plays an important role in the effective distribution of electricity across all the lighting systems of the house.
MCB can be used as an effective safety mechanism in small scale as well as large scale industries.
MCB is also used in heaters.
MCB can be easily used along with a ground fault mechanism.

Note:
In this question, we need to focus on the fact that MCB is an automatic switch or electromechanical device which is generally used instead of fuse nowadays.
In the condition of excess current it becomes turned off, making the circuit open. So our appliance is also safe from any damage.