International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is electric current defined as?

1. The flow of protons in a circuit

2. The flow of neutrons in an atom

3. The rate of flow of charged particles, such as electrons

4. The energy transferred in circuits

The correct answer is: The rate of flow of charged particles, such as electrons

Electric current is defined as the rate of flow of charged particles, such as electrons. In conductive materials like metals, it is primarily the electrons that move and create an electric current when a potential difference (voltage) is applied across a circuit. Current can be understood as a measure of how much charge passes through a given point in the circuit per unit time, which is usually expressed in amperes (A). This definition underscores the importance of charged particles in facilitating the flow of electricity, rather than focusing on other particles within an atom, such as protons or neutrons. Other options diverge from the definition of electric current. The flow of protons is not relevant in standard electrical circuits, as they are typically bound within atomic nuclei and do not move through a circuit like electrons do. Neutrons play no role in electrical conduction at all, as they are neutral particles and do not contribute to electric charge flow. Similarly, energy transfer in circuits pertains to different concepts, such as power and work done by the current, but does not specifically define what electric current is. Therefore, focusing on the flow of charged particles encapsulates the essential idea of electric current.