Electrical lamp circuit experiment. Classroom demonstration of electrical conductivity using a simple electric lamp circuit. Power is supplied by the battery, and wires and crocodile clips form the circuit with the electric light bulb (upper right). The paper-clip completing the circuit is metal and conducts electricity, hence the light bulb is lit. If this is replaced by non-conducting materials such the plastic ballpoint pen casing, or the string, the lamp will not light up. The aluminium foil (lower right) is a metal and will conduct electricity.