Electromotive force (EMF), often denoted as “ε” or “E,” is a concept in physics and electrical engineering that describes the electrical voltage or potential difference generated within a source of electrical energy, such as a battery or generator. EMF represents the energy per unit charge that is supplied by the source to maintain a flow of electric current in a closed circuit.

Here are key points about electromotive force (EMF):

  1. Source of Energy: EMF represents the work done by an energy source, per unit charge, to move electric charges around a closed circuit. It is a measure of the energy supplied by the source to overcome resistance and maintain current flow.
  2. Units: The unit of EMF is the volt (V), which is equivalent to joules per coulomb (J/C). This unit reflects the energy supplied (in joules) per unit charge (in coulombs) to the circuit.
  3. Direction: EMF has a specific direction in a circuit, determined by the orientation of the energy source. It is the force that pushes positive charge carriers (typically protons or holes) from the lower potential side to the higher potential side of the circuit.
  4. Not a Force: Despite its name, EMF is not an actual force but rather a potential difference or voltage. It represents the potential energy difference between two points in a circuit.
  5. Internal Resistance: Real-world energy sources, such as batteries and generators, often have internal resistance. This internal resistance can cause a voltage drop within the source itself when current flows, reducing the effective EMF delivered to the circuit.
  6. Conservation of Energy: EMF is governed by the principle of conservation of energy. The energy supplied by the source is equal to the energy dissipated in the circuit due to electrical resistance and other factors.
  7. Direction of Current: The direction of current flow in a circuit is opposite to the direction of the EMF. This is because current consists of negatively charged electrons, which move from higher potential to lower potential.
  8. Symbols: EMF is typically represented by the symbol ε (epsilon) or E. It is also sometimes denoted as “V” when discussing voltage.
  9. Applications: EMF is fundamental to the operation of electrical and electronic devices, from powering everyday batteries to generating electricity in power plants. It is essential for maintaining the flow of electric current in circuits.
  10. Measurement: EMF can be measured using a voltmeter, which is connected across the terminals of the energy source. The voltmeter measures the potential difference or voltage provided by the source.

In summary, electromotive force (EMF) represents the energy per unit charge supplied by an energy source to maintain electric current in a closed circuit. It is a fundamental concept in electricity and plays a crucial role in powering various electrical devices and systems.