Question

A small circular thing you push to active a machine

Answer 1

It might be the starting button of the machine.

You can push the starting button of a machine to activate the machine.

Even if the machine is an electric device then it can be the power source and you can start the machine by pushing the main power switch.

So it depends on the nature of the machine.  

Answer 2

hey!

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A small circular thing that we push to active a machine can be it's starting button .

All it depends upon the nature of the machine that we are using .

This requires a small force or if it is electronic machine

Then we have no need to have use power or something else .

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