Question

Question 13
Paheli set up an experiment using liquid A in the beaker as shown in the figure. She observed that the bulb glows. Then she replaced the liquid A by another liquid B. This time the bulb did not glow. Boojho suggested replacing the bulb by an LED. They observed that the LED glows. Explain.

Answer 1

Liquid A is a good conductor of electricity and it allows the maximum current to pass through it which is sufficient to glow the bulb.
But when it is replaced by another liquid B, the bulb does not glow because the current through liquid B could be weak and therefore unable to make the bulb glow.
But the small current which is passing through B is sufficient to glow a low voltage LED, so it glows.