In a circuit where three bulbs are connected in series, the positive terminal of the power source is connected to one end of the first bulb, and the negative terminal is connected to one end of the third bulb. The other end of the first bulb is connected to one end of the second bulb, and the other end of the second bulb is connected to one end of the third bulb, completing the circuit. The bulbs will share the voltage of the power source, and the total resistance of the circuit will be the sum of the resistance of each bulb. This means that the bulbs can dim or even turn off if one of the bulbs burns out, as the circuit will then be broken.
