General Certificate of Secondary Education (GCSE) Design Technology Practice Exam

In a circuit with back electromotive force (back EMF), the behavior of voltage is influenced by the inductance of the circuit components, such as motors or coils. Back EMF is generated when the current in a coil changes, such as when a motor slows down or speeds up. This induced voltage opposes the change in current, effectively creating what might be viewed as unwanted or additional voltage values in the circuit.

When back EMF is present, it can lead to scenarios where the total voltage in the circuit can exceed what might be expected based solely on the supplied voltage, especially when considering the voltage drop across other components. This can lead to voltage spikes or fluctuations that can be undesirable, particularly in sensitive electronics.

In contrast, in scenarios where voltage increases steadily or remains constant, the influence of back EMF is not appropriately accounted for, as the dynamic nature of electromagnetic induction affects voltage levels directly related to the current change rates. Thus, the presence of back EMF contributes to the potential for generating these unwanted voltage values within the circuit.