How do you know if bulb is burnt out?

To determine if a bulb is burnt out, first, check if the light fixture is receiving power by testing it with another working bulb or checking the circuit breaker. If the bulb is cool to the touch and does not light up when switched on, it may be burnt out. Additionally, inspect the filament inside an incandescent bulb; if it’s broken or discolored, the bulb is likely dead. For LED bulbs, look for any signs of damage or flickering, which may indicate failure.