A battery is a pump, wires are pipes, and electric charge flows around the loop like water. A bulb is a narrow, hardworking stretch of pipe that glows from the effort. Break the loop anywhere and everything stops at once.
What's actually happening
The single most useful picture in electricity is plumbing. The battery is a pump that pressurises charge; voltage is that pressure; the wire is fat, easy pipe; and every useful device — bulb, motor, heater — is a narrow constriction where the flow has to work to get through. The current is how much charge flows per second, and it's the same all the way around the loop, because charge has nowhere else to go.
Ohm's law is the whole relationship in one line: flow = push ÷ squeeze, I = V/R. Double the battery's push and the flow doubles. Double the squeeze and it halves. The work done in the squeeze — the glow of the filament, the spin of the motor — is power, P = V·I. Notably, nothing piles up and nothing is consumed: the same number of electrons leaves the battery's far end as entered the bulb. What the circuit "uses up" is the battery's ability to push.
And the loop explains the light switch, the most-used machine in your life. It doesn't ration electricity; it breaks the loop. Air is such a poor conductor that a millimetre gap stops the flow everywhere in the circuit, instantly — which is also why a single dead bulb in old-style fairy lights killed the whole string: one break, one loop, total darkness.
- 1Take a AA battery, a small torch bulb (or LED with a resistor), and a strip of kitchen foil folded into a ribbon.
- 2Hold the bulb's tip on the battery's + end and touch the foil from the bulb's side casing to the − end. Light.
- 3Now slide a strip of paper into any junction: dark — anywhere. The loop is everything.