Demonstration of the change in conductivity of a solution when a weak acid is added. In the solution are two wires, connected to a circuit containing a battery and a light bulb. If a current flows, the light bulb will light up. In this case it does not. Weak acids are those that do not dissociate much in solution, producing relatively few free ions. A current is the movement of charged ions, and the lack of ions here is seen in the lack of current flowing. For the same experiment with a strong acid, see clip K004 3150.