Four solutions, namely glucose, alcohol, hydrochloric acid and sulphuric acid filled in four separate beakers are connected one by one in an electric circuit with a bulb. The solutions in which the bulb will glow when current is passed are:

According to Activity 2.8, the glowing of a bulb in an electric circuit indicates that there is a flow of electric current through the solution. This current is carried through the solution by free ions.

• Hydrochloric acid ($\mathrm{HCl}$) and sulphuric acid ($\mathrm{H_2SO_4}$) dissociate completely in aqueous solution to produce hydrogen ions ($\mathrm{H^+}$) and corresponding anions ($\mathrm{Cl^-}$ and $\mathrm{SO_4^{2-}}$). These free-moving ions conduct electricity, causing the bulb to glow.
• Glucose and alcohol solutions do not dissociate into ions when dissolved in water. Since there are no free ions to carry the electric current, these solutions do not conduct electricity, and the bulb does not glow.

Therefore, the bulb will glow only in the beakers containing hydrochloric acid and sulphuric acid.