Automotive Electronics Practice Test

If one of the parking light bulbs in a parallel circuit burns out, what will Technician B claim about the current in the circuit?

1. It will increase

2. It will remain the same

3. It would decrease

4. It will stop completely

The correct answer is: It would decrease

In a parallel circuit, when one of the components fails, such as a parking light bulb burning out, the other components remain functional and continue to draw current. This means that the circuit has multiple pathways for current to flow; therefore, even if one pathway is interrupted (due to the burned-out bulb), the total resistance in the circuit changes. When a bulb burns out, it's as if that specific pathway is removed. The total resistance of the circuit increases because there are fewer pathways for the current to flow. According to Ohm's law, if resistance increases while the voltage remains constant, the overall current drawn from the power source will decrease. Thus, Technician B's claim that the current in the circuit would decrease is supported by the behavior of parallel circuits, where the failure of one path does not stop the entire circuit but alters the total resistance, leading to a reduction in current flow.