What is a Mechanical Switch?

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A switch which is operated mechanically to turn ON or OFF current in an electrical circuit is known as a Mechanical switch.

The familiar example of a mechanical switch is the tumbler switch used in homes to turn ON or OFF the power supply to various appliances such as fans, heaters, bulbs, etc.

The action of a mechanical switch can be beautifully understood by the schematic where a load RL is connected in series with a battery and a mechanical switch S.

As long as the switch is open, there is no current in the circuit.

When the switch is closed, the current flow is established in the circuit.

It is easy to see that the whole current flows through the load as well as the switch.

Limitations of Mechanical Switch

A mechanical switch suffers from the following three main drawbacks.

  1. In the closed position, the switch carries the whole of the load current.
    For a large load current, the switch contacts have to be made heavy to enable them to carry the necessary current without overheating.
    This increases the size of the switch.
  2. If the load current carried by the circuit is large, there will be sparking at the contacts of the switch during breaking operation.
    This results in the wear and tear of contacts.
  3. Due to the high inertia of a mechanical switch, the speed of operation is very small.

Due to above limitations, the use of mechanical switches is restricted to situations where switching speed is small and the load current to be handled is not very heavy.

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