A Level Physics Practice Exam

What is the main difference between emf and potential difference (pd)?

1. Emf converts chemical energy to electrical, while pd converts electrical energy to other forms

2. Emf and pd are essentially the same

3. Emf is associated with capacitance, while pd is not

4. Emf is always larger than pd in circuits

The correct answer is: Emf converts chemical energy to electrical, while pd converts electrical energy to other forms

The correct answer highlights a fundamental difference between electromotive force (emf) and potential difference (pd) in electrical circuits. Emf refers to the energy supplied by a source, such as a battery, which converts other forms of energy, like chemical energy, into electrical energy. This is the maximum potential difference supplied by the source when no current is flowing through the circuit. On the other hand, potential difference occurs across components in a circuit when current is flowing and is the energy used by the charge carriers as they move through the circuit, often converting electrical energy into other forms, such as heat, light, or mechanical work. This distinction helps clarify how energy is transformed and utilized within electrical circuits, making choice A a comprehensive explanation of the main difference between emf and potential difference.