Science in Punggol study guide · Article 0009 of 20

A bulb in a simple circuit lights when suitable working components form a complete conducting path through the bulb. An open switch breaks that path, so current cannot flow around the circuit.

Having a cell, wires and a bulb is not enough. Their connections must allow current to travel through the intended circuit and return to the cell’s other terminal.

On this page: Know the role of each part · Trace the complete path · Check a fault one step at a time · Worked question

Know the role of each part

The cell supplies electrical energy. Wires provide conducting connections. A switch can complete or break the path. The bulb converts electrical energy into light and heat energy.

These parts work together. A working cell cannot make a bulb light if the path is broken. A complete-looking arrangement may still have a loose connection or an unsuitable component.

For a practical activity, use low-voltage equipment intended for school circuit investigations and follow adult guidance. Household sockets and mains wiring are not suitable materials for a child’s experiment.

Trace the complete path

Begin at one terminal of the cell. Follow the conducting connection through the bulb and back to the other terminal. Look for an unbroken path through the parts that should carry current.

One wire touching a bulb is not enough without a return connection. Parts placed next to each other are not necessarily connected. A wire’s conducting end must make proper contact with the intended connection point.

A closed switch joins the path. An open switch leaves a gap. In a diagram, the switch’s position matters more than how neatly the arrangement is drawn or whether it looks like equipment on a desk.

Cells are not containers of current that empty into the bulb. Their stored chemical energy supplies electrical energy as the circuit operates. The bulb converts energy; it does not consume the current.

Check a fault one step at a time

A bulb that does not light gives an observation, but not an immediate answer about its cause. The path might be broken, a contact might be poor, the cell might be unable to supply enough energy, or the bulb might be damaged.

Check one relevant thing at a time. Replacing every component at once may restore the light, but it will not identify the original fault. Inspect connections first, then test a suspect part in a known working arrangement.

A complete path alone does not guarantee that every possible circuit will work. The source and components must be suitable and contacts must conduct properly. In a written question, use its stated conditions rather than inventing an extra fault.