NOCTI Diesel Technology Practice Test

Lights wired in parallel share the same two connection points to the power source, so each branch experiences the same voltage. That means the voltage across every bulb in a parallel circuit is identical, even as you add or remove bulbs. If one bulb burns out, the others stay lit because each bulb has its own path to complete the circuit; removing one path doesn’t interrupt the others. The current in each branch depends on that branch’s resistance and the shared voltage, so the current in a single branch isn’t equal to the total current—the total current is the sum of all branch currents. Because the voltage across each bulb remains the same, their brightness stays the same in an ideal power supply; adding more bulbs just draws more total current, not brighter bulbs.