Differences between Potential Difference and Electromotive Force

Potential difference across two ends of a conductor causes the dissipation of electrical energy into other forms of energy. The agency which provides the potential difference for the steady flow of current is the battery. Current flows through a conductor as long as there is a potential difference. E.m.f is the energy supplied by a battery to a unit charge as it flows through a closed circuit or the energy converted from non-electrical forms to electrical form when one coulomb of positive charge passes through the battery. The flow of charge through a circuit is responsible for the presence of e.m.f.

Potential Difference

When current flows through the conductor, it experiences a resistance in the conductor. The energy supplied by the battery is utilized in overcoming this resistance and is dissipated and other forms of energy. It can be measured by a voltmeter connected directly across the terminals of the component. To measure the potential difference, the resistance of the voltmeter must be very large so that no current passes through it. The polarity must be kept in mind in order to measure the potential difference. The positive terminal of the cell is connected to the positive terminal of the voltmeter and the negative terminal of the cell is connected to the negative terminal of battery. Its unit is Volt (V).

Electromotive Force (e.m.f)

For the continuous flow of current through a wire, battery supplies energy to the charges. These charges leave positive terminal and reach the negative terminal.  The battery supplies energy to the charge at lower potential i.e. negative terminal. Its unit is J/C. It can be measured by a voltmeter connected directly with the terminals of the battery when no current is flowing through the circuit.

Potential Difference VS Electromotive Force

Definition:

Potential difference is the dissipation of electrical energy into other forms of energy.

E.m.f is the energy converted from the other forms of energy into electrical energy as one coulomb of charge passes through the battery.

Source:

Potential difference is of conductor.

E.m.f  is of battery.

Relationship with flow of current:

Potential difference is zero when no current flows.

E.m.f. is not zero when no current flows.

Unit:

Unit of potential difference is Volt (V).

Unit of e.m.f is J/C.

Measurement:

To measure potential difference, voltmeter is connected in parallel with the device across which the potential difference is to be measured.

To measure e.m.f. the voltmeter is connected in series in the circuit.

Cause/Effect:
Potential difference is the cause of current. A current flows due to the presence of potential difference.

E.m.f is the effect of current.

Function:

Potential difference is required to allow the charge to travel from higher potential to lower potential i.e. from positive terminal to negative terminal.

E.m.f. is required to send the charge from lower potential to higher potential i.e. from negative terminal to positive terminal.

Conclusion

Potential difference is responsible for the flow of current while electromotive force (e.m.f) is responsible for continuing the flow of current.