## Lights, Sound, Action!

Skills
observing
communicating
comparing
applying
problem solving

Materials
3 D-cell batteries
2 flashlight bulbs (at least 3 volt)
5 pieces of insulated copper wire 12-15 cm (5-6 inches long)
2 bulb holders
buzzer
tape
4 alligator clips

Doing the Activity

1. From your materials take a battery, light bulb, and bulb holder, and two pieces of copper wire. Make sure that 1.5 cm (1/2 inch) of insulation has been stripped from each end of the wires so that you can make the connections.

2. Carefully screw the bulb into the holder. Connect one end of each wire to each of the two clips on the bulb holder.

3. Connect the loose ends of one wire to the battery. (Use tape to hold the wires in place, if needed.) When the bulb lights, the path you have made with your connections is called a complete, or closed circuit.

4. Each group now needs two batteries, two bulbs, two bulb holders and four wires. Try to make two bulbs light at the same time. When you wire a circuit so that electricity flows first through one bulb and then through the second, you get a series circuit.

5. Follow this diagram. When each bulb has a separate circuit, we say the circuit is a parallel circuit. You have given each bulb its own circuit.

Talking it over

• To light the bulb, does it matter which direction the positive or negative end of the battery is pointing?
• Observe what happens when you unscrew one bulb in a series circuit. Why did that happen?
• When you used two or more bulbs in your series circuit, did the additional bulbs burn as brightly as in the circuit made with just one bulb? Did all the bulbs in your series circuit glow with the same brightness? Why or why not?
• If our homes were wired in series, what would happen as we turn on more and more lights and appliances? Why?
• When you use a parallel circuit, do all bulbs burn with the same brightness? Are they brighter or dimmer than they were in your series circuit? Why?
• Suppose you had a string of patio or Christmas tree lights plugged in and one bulb burned out. What would happen to the other bulbs if your lights were wired in series? In parallel? Which kind of wiring for the lights do you think would be better to use? Why?
• Name at least one advantage and one disadvantage of electrical wiring done in parallel and done in series.

What's Happening
Electricity is a form of energy that comes from the movement of electrons. Electrons are tiny particles in any atom. Since electrons are negatively charged particles, they are attracted to positively charged objects and are repelled by negatively charged objects, including other electrons. Movement of electrons creates an electrical current. The unbroken path or loop through which electricity flows is called a complete or closed circuit. If the electricity does not flow at all, then we know there is a break in the circuit, or an open circuit. What happens to the circuit when you turn off a light switch? When you turn on a switch, the break is closed and the electric current can now travel through the wire to a light a bulb, buzzer a buzzer, or turn a fan. Circuits can be wired in a series or in parallel. In series wiring, there is only one path for the electrons to follow. In a circuit made from batteries, wires, and more than one bulb, the electrons must travel through all the bulbs to complete the circuit. In parallel wiring, the electrons have more than one path in which they can travel. Now when one bulb is disconnected, other paths are still unbroken.

More Challenges
Make a circuit that produces light, sound, and motion all at once! Is it wired in series or in parallel?

Activity Source
"Funtivities: Hands-on Science and Math." Iowa State University Program for Women in Science and Engineering. Extension Distribution Center