light from a bulb gets dimmer for a moment , when geyser isnswitched on why
The bulb gets dimmer because of fall in the potential across the bulb.
Cause of fall in potential
Every house wiring has some resistance. When the bulb was connected without the geyser the potential difference across its end was nearly same as the source. Now when geyser was turned on the resistance due to the geyser and the bulb starts to act parallel and hence equivalent resistance of the circuit decreases.
Decrease in the total resistance of the circuit leads to an increase in the current of the circuit. Now the as more current flows through the resistance of the wiring, greater potential drop due to the wiring is created. This potential drop due to the wiring of the house leads to a fall in the potential across the bulb.
Had the wiring been of 0 resistance we won’t have seem the bulb glow dim.
We know that the geyser and the bulb are connected in a parallel circuit.
So in a parallel one the current distributed to different appliances in directly proportional to the resistance of that appliance. So, when geyser is switched on it derives a larger current from the circuit and the bulb dims for a second.....
Hope this helps...