Mention the condition under which charges can move in a conductor. Name the device which is used to maintain this condition in an electric circuit.

(N/A) Charges can move in a conductor only if there is a potential difference across its two ends. This potential difference is necessary to create an electric field that exerts a force on the charges,causing them to flow. The device used to maintain this potential difference in an electric circuit is an electric cell or a battery (a combination of one or more cells).