photo of the visual electricity demonstratorApparatus:



Can be used to clarify several important concepts, such as:

- Charged particles exist in the wire before the current starts to flow

- Charged particles in complete circuits move at finite, observable speed -    not the speed of light.

- When voltage is applied to a complete circuit, particles at all points in        the circuit begin moving instantaneously and simultaneously.

- Charged particles in complete circuits can flow in a single direction            (direct current) or back and forth (alternating current).