When an aqueous solution of HCl was taken in the beaker, and the circuit was closed, the bulb in the circuit began to glow, but it did not glow when the experiment was repeated with glucose solution because:

HCl is an acid which gets ionized into H⁺ and Cl^- ions. As we all know ions are the main responsible for the conduction of electricity. As a result, the circuit becomes complete, and bulb starts to glow.

On the other hand, glucose is not and acid. It does not get ionized because it is a carbohydrate and a covalent compound. As we know covalent compounds do not conduct electricity due to the absence of ions in them. Therefore, the bulb does not glow.

i) In the presence of NaOH, yes the bulb will glow because NaOH being a strong base gets ionized into Na⁺ and OH^- ions. These ions are responsible for the conduction of electricity. As a result, the bulb will start to glow.

ii) In the presence of NaCl, yes the bulb will glow because NaCl being a common salt gets ionized into Na⁺ and Cl^- ions. These ions are responsible for the conduction of electricity. As a result, the bulb will start to glow.