Question

what is the p.d.across the battery?​

Answer 1

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Potential difference (V) is measured in volts (V). Potential difference is the work done per unit charge. A potential difference of 1 V means that 1 joule of work is done per coulomb of charge. Potential difference is the work done in moving a unit of positive electric charge from one point to another.

Answer 2

Explanation:

When you measure the potential difference across (or between) the terminals of a battery that is not in a complete circuit you are measuring the emf of the battery. This is the maximum amount of work per coulomb of charge the battery can do to drive charge from one terminal, through the circuit, to the other terminal.