Question

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

Answer 1

LED v/s bulb

1. Light-emitting diodes, or LEDs, are semiconductor light-emitting sources that emit light when current is sent through them.
2. Electrons recombine with electron holes in semiconductors, producing energy in the form of photons.
3. It's a sort of diode that shares many of the same features as a p-n junction diode. This means that an LED permits electricity to flow in one direction but prevents it from flowing in the opposite direction.
4. LED use much less energy than incandescent bulbs because diode light is much more efficient, power-wise, than filament light.
5. A normal bulb cannot convert very little electrical energy or voltage to light energy, whereas an LED can. LED lights are able to illuminate in liquid B even with the low current flow.

Hence, the current through liquid B could be weak and therefore unable to make the bulb glow. However, it was strong enough for the LED to glow.