Which instrument is used to measure electric current?

$(a)$ Define the term 'volt'.
$(b)$ State the relation between work,charge,and potential difference for an electric circuit. Calculate the potential difference between the two terminals of a battery,if $100 \ J$ of work is required to transfer $20 \ C$ of charge from one terminal of the battery to the other.

$1 \; kWh = \ldots \ldots \ldots \; \text{watt-seconds}$

No current flows between two charged bodies when connected,if they have the same

Electric power is also called $BOTU$.

What will happen to the resistance of the circuit,if the current through it is doubled?