Circuits, symbols and brightness
Physics · Key Stage 2 · The School
Drawing a circuit properly
Scientists draw circuits with agreed SYMBOLS so that any reader anywhere understands the diagram: a cell as one long and one short line, a lamp as a circle with a cross, a switch as a line that lifts away from a contact, a buzzer, a motor. Wires are drawn as straight lines with square corners. A drawing of the actual tangle of wires is slower to draw and harder to read.
More cells, brighter lamp
Add a second cell and the lamp glows brighter and the buzzer sounds louder, because more cells push the current round harder. Add more lamps to the same circuit instead and each one dims, because they share the same push. Change a component for one with a different rating and it will behave differently in the same circuit — which is why a bulb from a torch may barely glow on a single cell.
When it does not work
A circuit only works if it is COMPLETE — an unbroken loop from one end of the cell back to the other. That is exactly what a switch controls: closed completes the loop, open breaks it. Most non-working circuits are a loose crocodile clip, a flat cell, a blown lamp, or a gap you cannot see. Check the loop first, one connection at a time.
Build a circuit with one cell and one lamp and note the brightness. Add a second cell in series: the lamp is noticeably brighter, because there is more push. Now go back to one cell and add a SECOND lamp in series: both lamps are dimmer than the single one was, because the same push is now shared between two. Predict each stage before you build it — that is where the learning is.