Trace the device, not just the loop
Imagine a device connected between two points on a circuit. Now add a wire directly between those same points. That wire provides a bypass: a conducting route around the device. A short circuit usually means an unintended path with very low resistance. An open circuit is different: it interrupts a route rather than adding one.
“Electricity takes only the shortest path” is a misleading rule. Parallel paths can both carry current. Their resistances and the voltage across them determine how much. A long, thick wire can have less resistance than a short, thin one; the shape drawn on a board does not settle the question.
One source, two very different results
Our example gives a 6 V source an internal resistance of 1 Ω and connects an 11 Ω device. With no bypass, the total resistance is 12 Ω. The current is 6 ÷ 12 = 0.5 A. The device’s voltage is 0.5 × 11 = 5.5 V, and its power is 5.5 × 0.5 = 2.75 W.
Close an ideal wire across the device and both ends of the device become the same electrical point. Its voltage drops to zero. The source still has its internal 1 Ω, so source current becomes 6 ÷ 1 = 6 A. That current does not mean the bypassed device is working harder: its power is now zero.
Why the model needs a limit
An ideal voltage source connected to an ideal zero-resistance wire produces an impossible unlimited-current calculation. Including a source resistance avoids that contradiction. Real batteries, wiring and protection have further limits; heating can be dangerous. This example explains a pattern, not the temperature or safety of real equipment.
Keep all testing on this page or in the browser game. A glowing part, a shut-down source, and a dark bypassed device can be different consequences of a circuit fault. Check the feedback rather than judging the result from brightness alone.
Take the trace into Spark Island
In Spark Island, start at the labelled battery terminals and trace a route through the part named in the mission. Look for an extra connection joining two points that should be separated by that part. The game’s mission requirements and safety feedback take priority over this page’s simplified numbers.
Before deleting a wire, say what you expect to change. Then remove just that wire and run again. Did the intended device enter the useful path? Can you explain why the extra wire prevented the intended result? That explanation is more useful than remembering a particular arrangement of coloured lines.
Source & scope
OpenStax: Electric Hazards and the Human Body. Background on low-resistance faults and electrical hazards. The numerical example and interactive model above are original teaching examples.
This is an Aurism learning article, with AI-assisted development as described in our editorial approach. It does not claim an independent expert review or that a simplified model reproduces every game outcome. Report a correction.
TRY THE IDEA IN A GAME
Spark Island
Use the mission’s actual instructions and feedback to test your next prediction.