Aligned with NGSS Performance Expectation: HS-PS3-3
Investigate the energy transfer and circuit topography of two stage lighting tracks.
When wiring multiple electrical devices (like stage lights) to a single power source, there are two primary ways to arrange the circuit: series and parallel. This simulation demonstrates the profound differences in energy transfer and reliability between these two topologies, which is a key concept in physics and engineering.
In Track A (Series Circuit), the bulbs are wired end-to-end in a single continuous loop. This means the current has only one path to flow through. Because of Ohm's Law (V = I·R), as you add more bulbs (increasing the total resistance R), the total current (I) decreases. Furthermore, if the bulbs are identical (that is, have equal resistance), the voltage from the power source is divided equally among them. This leads to a critical flaw for lighting: as you add more bulbs, the voltage and power (P = I·V) available to each individual bulb drops dramatically, causing them all to become dimmer. If one bulb were to break (try clicking one!), the entire circuit is interrupted, and all lights go out.
In Track B (Parallel Circuit), each bulb has its own direct, independent connection to the power source. This means every bulb receives the full 120 V from the source, regardless of how many other bulbs are connected. Because the voltage remains constant for each bulb, they all shine at full brightness no matter how many are added. Also, if one bulb breaks, the others remain lit because they have their own unbroken paths to the power source. However, this convenience comes with a trade-off. As you add more parallel branches, the total resistance of the entire circuit decreases, which causes the total current drawn from the source to increase significantly.
This increasing current is why homes and venues use Circuit Breakers. In Track B, if you add too many bulbs, the total current will eventually exceed the safe limit of the wiring (in this case, 20.0 Amps). When this happens, the circuit breaker deliberately "trips" (opens the circuit) to prevent the wires from overheating and causing a fire.