Difference Between Watts and Volts

Main Difference – Watts vs. Volts

Watts and volts are both units used in measurements involving electric currents. The main difference between watts and volts is that watts are a unit for measuring power, whereas volts are a unit for measuring the electric potential difference.

What is Volt

When an electric current flows around a circuit, electrons gain energy as they go through cells or generators, and they lose this energy as they go through loads that have resistance. Electric potential refers to the amount of electrical energy that a coulomb of electrons contains (a “coulomb” of electrons consists of 1.6×10¹⁹ electrons). The volt is the SI unit for measuring electric potential. The unit is named after the Italian scientist Alessandro Volta (1745–1827), who invented the voltaic cell. The symbol for volts is V.

Alessandro Volta

What is Watt

Watts measure electric power. Power measures the amount of energy that is transferred per unit time. If a current $I$ flows through two points in a circuit that have a potential difference of $\Delta V$ between them, then the total number of charge that flows between the two points in a time $t$ is $It$ (in coulombs). Since each coulomb of charge loses an energy $\Delta V$ as it flows between the two points, the total energy dissipated is $\Delta VIt$ . Then, the amount of energy dissipated per unit time, i.e. the power dissipated, is given by:

$P=VI$

Watts are the SI unit for measuring electric power. Watts are named after the Scottish Engineer James Watt (1736–1819), the inventor of the Watt steam engine. The symbol for watts is W.

James Watt

Base Units for Volts and Watts

Voltage is a quantity of energy divided by a quantity of charge. Energy (work) is a product of force and distance. At the same time, charge is a product of current and time. So, in terms of units,

$\mathrm{V=\frac{J}{A\cdot s}=\frac{N\cdot m}{A\cdot s}}$

Since force is a product of mass and acceleration,

$\mathrm{V=\frac{kg\cdot m\cdot s^{-2}\cdot m}{A\cdot s}=kg\cdot m^2\cdot A^{-1}\cdot s^{-3}}$

As we have seen earlier, power can be written as a product of potential difference and current. So, the base units of watts is:

$\mathrm{\left( kg\cdot m^2\cdot A^{-1}\cdot s^{-3}\right)\cdot A=kg\cdot m^2\cdot s^{-3}}$