Automotive Electronics Practice Test

What is the outcome when two bulbs with different resistances are connected in parallel to a 12 volt battery?

1. Only the 2 ohm bulb will light

2. Both bulbs will light up equally

3. Both bulbs will be equally bright

4. Only the 6 ohm bulb will light

The correct answer is: Both bulbs will light up equally

When two bulbs with different resistances are connected in parallel to a 12-volt battery, both bulbs will light up because they are connected directly across the same voltage supply. In parallel circuits, the voltage across each component is the same; in this case, it is 12 volts for both bulbs regardless of their resistance values. The current flowing through each bulb can be determined by Ohm's law (I = V/R). For a 2-ohm bulb, the current will be 6 amps (12V / 2Ω), while for a 6-ohm bulb, the current will be 2 amps (12V / 6Ω). Each bulb will indeed receive the full 12 volts, allowing both to illuminate. However, the brightness of each bulb will differ because it depends on the power consumed by each bulb, given by the formula P = V²/R. The 2-ohm bulb will have a power of 72 watts (12² / 2), while the 6-ohm bulb will have a power of 24 watts (12² / 6). Consequently, the 2-ohm bulb will be brighter than the 6-ohm bulb since it consumes more power. In summary,