Experiment 5
Bulbs in series divide the applied voltage. What about bulbs in parallel? Let's try an experiment.
STEP 1. Arrange three bulbs in parallel. See the picture and diagram below.
Notice that the positive is connected to one side of each bulb and the negative is connected to the other side of each bulb.
STEP 2. Attach 3 volts to the circuit and observe the brightness of the bulbs.
Discussion. In a parallel circuit, all the bulbs "see" the full voltage. Each bulb has 3 volts so they each burn brightly just as one would burn brightly with 3 volts. What is the advantage of this arrangement? Try removing one bulb from the circuit. Does it have any impact on the others?
A series string will fail if one light fails, but a parallel string will continue to operate with one or more lights out.
Advantages/Disadvantages of a parallel system:
1. The lights do not fail if one light fails
2. The power source needs to equal the appropriate voltage of the bulb, around 3 volts for mini lights. This requires an additional power supply and is inconvenient for something you want to just plug in.
3. Requires more wire.
Advantages/Disadvantages of a series system
1. Generally one can have a string of 50 lights and plug it into a 120 source. Each bulb "sees" about 2.4 volts.
2. It is cheap! Fewer feet of wire.
3. If one bulb blows, you must determine which bulb is bad.
Electronic Tricks
Most newer strings of lights are equipped with bulbs that have an extra wire around the base of the bulb called a shunt. When a light is shattered or burned out, the light string will continue to operate because the extra wire conducts electricity in the series.
