A student performs an experiment and took 4 test tubes A, B, C and D, containing glucose solution, alcohol solution, sulphuric acid solution and sodium hydroxide solution respectively. Then to each beaker, a bulb and battery are connected and then the current is passed. In which of the test tubes, the bulb will glow?

Glucose and alcohol are non-electrolytes, thus they do not dissociate into ions when dissolved in water. On the other hand, sulphuric acid releases free hydrogen ions and sodium hydroxide solution releases free hydroxide ions. The free ions carry the electric charge and hence are responsible for the conduction of electricity in acids and bases.

Thus, both C and D bulb glows as they have solutions that are good conductors of electricity.