How is electromotive force (emf) different from voltage?

Electromotive force (emf) is the energy provided per unit charge, while voltage is the energy used per unit charge.

Electromotive force, often abbreviated as emf, is a concept in physics that refers to the amount of energy provided by a source (like a battery or generator) per unit charge. It's essentially the 'push' that drives electric charges around a circuit. The term 'force' in emf is a bit misleading, as it's not a force in the traditional sense, but rather a type of potential energy. It's measured in volts, just like voltage, but the two are not the same thing.

Voltage, on the other hand, is a measure of the energy used per unit charge as it moves around a circuit. It's the 'drop' in energy experienced by charges as they pass through components in a circuit, like resistors or light bulbs. Voltage is also known as 'potential difference', as it represents the difference in electric potential between two points in a circuit.

The key difference between emf and voltage lies in their roles in an electrical circuit. Emf is the energy supplied to the charges, while voltage is the energy used by the charges. In a perfect, resistance-free circuit, the emf and voltage would be equal, as all the energy supplied by the source would be used by the charges. However, in real-world circuits, some energy is always lost due to resistance, meaning the voltage is always less than the emf.

In summary, while both emf and voltage are measures of energy per unit charge and are measured in volts, they represent different aspects of electrical energy in a circuit. Emf is the energy supplied, while voltage is the energy used. Understanding this distinction is crucial for a thorough understanding of electric circuits in physics.