By Stephen Benham, Updated Aug 30, 2022
Electrical circuits allow electricity to travel from a power source—such as a battery—to a device and back again. By experimenting with different wiring configurations, students can observe how voltage and current behave, making for an engaging science‑fair exploration.
Parallel wiring is common in household circuits because it keeps the voltage unchanged while increasing total capacity. For a fifth‑grade project, pair two identical batteries. Connect the positive terminal of the first battery to the positive terminal of the second, and do the same for the negative terminals. Attach a light bulb to the combined terminals of the parallel pair and note how long it illuminates. Then wire a single battery of the same voltage to another light bulb. The parallel pair should power its bulb for roughly twice the duration of the single‑battery bulb, demonstrating doubled endurance.
A series connection adds the voltages of each cell while keeping capacity the same. For example, three 1.5‑volt cells produce 4.5 volts. Arrange the cells in a line, connecting the negative terminal of one to the positive terminal of the next. Use wires to complete the loop from the first cell’s positive terminal to the last cell’s negative terminal. When you connect a light bulb across these points, it receives the full 4.5‑volt supply, illustrating how series wiring boosts voltage.
By mixing series and parallel connections, you can achieve both higher voltage and greater endurance. Use four identical batteries: pair 1 with 2 in series, and pair 3 with 4 in series. Then connect the two series pairs in parallel. This configuration doubles the voltage of a single cell while also doubling its capacity. Wire a light bulb across the overall positive and negative terminals to observe the combined effect.
To compare the two arrangements, place the parallel pair and the series pair side by side, each powering its own light bulb. If you cut one wire from the series circuit, the bulb will go out immediately because the loop is broken. Cutting a wire between the parallel batteries will leave the other battery still supplying current, so its bulb remains lit. This simple test highlights the key difference: series circuits require a continuous loop, while parallel circuits allow each battery to operate independently.
