How is a voltmeter connected in the circuit to measure the potential difference between two points?

The electric potential difference between two points is defined as the work done to move a unit charge from one point to the other.

                                                           $\mathrm{V} = \mathrm{W}/\mathrm{Q}$

The SI unit of electric potential difference is volt (V).

where,

One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.

                                              $\therefore 1 \mathrm{volt} = \frac{1 \mathrm{joule}}{1 \mathrm{coulomb}}$

                                                      $1 \mathrm{V} = 1 {\mathrm{JC}}^{–1}$

The potential difference is measured by means of an instrument called the voltmeter. The voltmeter should be connected in parallel to measure the potential difference between two points.

Note: For a series circuit, voltmeters cannot be used. Instead, an ammeter is used in a series circuit.