Question

Why does an electric bulb become dim when an electric heater in parallel circuit is switched ON?

Answer 1

1. When a heater is switched on in parallel, the total current drawn from the source increases.
2. Due to internal resistance of the power supply or wiring, the voltage across each appliance may drop slightly.
3. As a result, less voltage is available across the bulb.
4. Lower voltage reduces the bulb’s brightness, making it appear dim.