Automotive Electronics Practice Test

Regarding two bulbs connected in parallel with a third added, which technician's statement is correct about brightness and current?

1. Technician A only

2. Technician B only

3. Both Technicians A and B

4. Neither Technician A nor B

The correct answer is: Neither Technician A nor B

In a parallel circuit, each component is connected across the same voltage source. Therefore, the voltage across each bulb remains consistent regardless of how many are added. Consequently, each bulb receives the same voltage, which typically results in them being equally bright if they are identical bulbs. When a third bulb is added in parallel, the total current drawn from the power source increases because the overall resistance of the circuit decreases. However, each individual bulb still receives the same voltage, thus maintaining the brightness of the existing bulbs. If both technicians made claims that contradict this behavior — such as suggesting that the brightness of the original bulbs decreases when a new bulb is added, or that the current through the original bulbs changes — these statements would be incorrect. In a parallel setup, adding more bulbs does not affect the voltage across any individual bulb but does lead to higher total circuit current. The conclusion is that, if both technicians did not accurately describe the behavior of the bulbs regarding brightness and current flow, then neither is correct.