Final answer:
For decoration lights, a parallel circuit is best because it keeps the strand lit even if one bulb goes out. In a series circuit, if one bulb burns out, it can cause the entire strand to go out. The operating voltage divides equally among the bulbs in both series and parallel circuits.
Step-by-step explanation:
For lights used in decorations such as holiday lights, a parallel circuit is advantageous because if one bulb in the circuit burns out, the rest of the strand will remain lit. This is because in a parallel circuit, each bulb has its own path to the power source, so the flow of electricity isn't interrupted by a single bulb's failure.
When discussing holiday light strands wired in series, the old version that used bulbs that break electrical connections would cause the entire strand to go out if one bulb burned out. In the scenario presented, if a string of 40 bulbs is designed for a 120 V power source, each bulb would typically operate at 120 V / 40 bulbs = 3 volts per bulb. If the newer version bulbs, which short circuit when they fail, burns out, the 120 V would be divided among the remaining 39 bulbs, resulting in an operating voltage of 120 V / 39 bulbs = approximately 3.08 volts per bulb.
Shunts in holiday light strings ensure the flow of current continues when a bulb burns out. However, if too many bulbs fail, the shunts themselves can fail, which occurs because the circuit wasn't designed to handle the extra current flowing through fewer bulbs, potentially causing the shunts to overheat and open.
In an example where three light bulbs are connected in a circuit, when one is removed or fails in a series arrangement, the other bulbs will not light up due to the interrupted circuit.
Household circuits typically use a combination of series and parallel wiring to operate efficiently, which involves critical infrastructure such as fire alarms being wired in series for reliability, while outlets are usually wired in parallel to ensure availability across multiple devices.
Incandescent light bulbs can be modeled as resistors, and when connected in series, the bulb with the higher resistance will typically be dimmer due to the lower current flow.