• When charge passes through a power supply such as a battery, it?gains?electrical energy
• The?electromotive force (e.m.f)?is the amount of?chemical?energy converted to?electrical?energy per?coulomb?of charge?(C)?when charge passes through a power supply
• e.m.f is measured in?Volts (V)

Definition of e.m.f with regards to energy transfer

• e.m.f is also the potential difference across the cell when no current is flowing
• e.m.f can be measured by connecting a high-resistance voltmeter around the terminals of the cell in an open circuit

e.m.f is measured using a voltmeter connected in parallel with the cell

• The difference between?potential difference?and?e.m.f?is the type of energy transfer per unit charge

Definition of potential difference with regards to energy transfer

• When charge passes through a resistor, for example, its electrical energy is converted to heat in the resistor
  • The resistor therefore has a?potential difference?across it
• Potential difference describes the loss of energy from charges; ie. when?electrical energy?is?transferred?to other forms of energy in a component
• e.m.f. describes the?transfer of energy?from the?power supply?to?electrical charges?within the circuit