$A$ battery is a source of maintaining a constant potential difference across two ends of a conductor.

What is a voltmeter? How is it connected in a circuit?

What is the device (meter) used to measure electric potential difference called?

Name the device/instrument used to measure potential difference. How is it connected in an electric circuit?

If $2 \times 10^{-3} \text{ J}$ of work is done in moving a particle carrying a charge of $10 \times 10^{-6} \text{ C}$ from infinity to a point $P$, what will be the potential at the point $P$ (in $\text{ V}$)?

Give a single word for $\frac{1 \text{ joule}}{1 \text{ coulomb}}$.