Unit of electromotive force is (1) volt (2) second (3) metre (4) \(\mathrm{ms}^{-1}\)

The volt, symbolized by the capital letter 'V', is the SI unit used to measure the potential difference (voltage) between two points in an electrical circuit. One volt is defined as the difference in electric potential that would drive one ampere of current against one ohm resistance. In other words, one volt is equivalent to one joule of energy per coulomb of charge.

When we say a battery has a voltage of 1 V, we mean that the battery can supply one joule of energy for every coulomb of charges that flow through the circuit. The name 'volt' comes from the Italian physicist Alessandro Volta, who invented the Voltaic pile, widely considered the first chemical battery. Understanding the volt is critical in comprehending how electromotive force operates in an electric circuit.

An electric circuit is composed of various components like batteries, resistors, capacitors, switches, and conductors that form a closed loop, giving a path for the electrons to flow. Circuits can be simple, containing a single light bulb and battery, or complex, comprising numerous components and loops.

The key function of an electric circuit is to transfer energy from a power source to a specific application or load. The circuit's design ensures the controlled flow of electrons in a particular direction, which is vital for the circuit to perform as intended. A crucial aspect of this is the concept of electromotive force or EMF, which can be thought of as the 'pressure' that pushes electrons along the wires of the circuit. Without a source of EMF, like a battery or generator, no current would flow, and the circuit would be non-functional.

Potential difference, often referred to as voltage, is the driving force behind the movement of electrons in an electric circuit. It is the measure of the work needed to move a charge from one point to another against an electric field. Think of it as how water pressure can push water through a pipe; potential difference does a similar job for electrons in a circuit.

The potential difference is what causes electrons to flow from a region of high electric potential to a region of lower electric potential. Measuring the potential difference in a circuit is key to determining how a circuit will function, as it influences the flow rate of the electric current, which is measured in amperes. Devices such as voltmeters are used to measure this potential difference in volts, and it's the very concept that ties together electromotive force and electric circuits.