Question

what produces an electric current in a circuit? How is it released?

Answer 1

Electrons.it's release by current.

Answer 2

When a battery is attached to the electric circuit, the flow of elections or electric charges in it produces an electric current in it.

Electric current can also be produced in a circuit without battery by means of magnets.
This is known as electro-magnetic induction. In this process an induced current is produced when a magnet is put towards the electric circuit.

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