Parallel: What is a Parallel Circuit and How Does it Work?

Problem

What is a parallel circuit and how does it work?

Materials

• 4 12-inch (30-cm) strips of aluminum foil
• new, clean penny
• duct tape
• size D battery
• short, wide rubber band
• 2 flashlight bulbs paper clip
• helper

Procedure

1. Wrap the end of one foil strip around the penny, and tape the foil-wrapped penny to the negative terminal of the battery.
2. Tape the second foil strip to the positive terminal of the battery.
3. Stretch the rubber band around the battery to hold the coin and strips tightly against the battery ends.
4. Twist one end of each remaining foil strip tightly around the base of a flashlight bulb.



5. Use the paper clip to attach the free ends of the remaining foil strips to the foil strip attached to the negative terminal end of the battery.
6. Rest the metal tips of the bulbs on the foil strip attached to the positive terminal of the battery.

Results

Both bulbs glow with the same brightness. If either bulb does not glow, then:

• Check all connections.
• Ask a helper to hold the metal strips tightly against the ends of the battery.
• Be sure the metal tips on the bulb are clean.
• Replace the bulb that does not glow; it may be burned out.

Why?

When an electric circuit provides more than one path for electric current to follow through, the circuit is called a parallel circuit .The characters in the diagram on below represent charges moving through a parallel circuit. The electric current leaves the negative terminal of the battery and arrives at point A, where it separates into two different paths. At point B, the divided current combines again and flows into the positive terminal of the battery. Even though the current divides and takes different paths, the "push" or voltage of the current is the same in each path; thus, the two light bulbs connected in a parallel circuit glow with equal intensity.

Let's Explore

Would changing the number of light bulbs affect the results? Repeat the experiment several times, increasing the number of bulbs by one each time until there are a total of four to six bulbs all connecting in parallel with each other. Helpers will be needed to assist in holding the extra bulbs in place. Science Fair Hint: Display diagrams and models of the circuits constructed.

Show Time!

1.  
   1. When one light in your home or school burns out or is turned off, all of the other lights stay on because they are connected in a parallel circuit. Ask an electrician to help you design and construct a small model of a two-or three-room building using flashlight bulbs for ceiling lights and batteries to provide the power. Switches for the lights and room furnishings will make this an even more presentable project display.
   2. Electricians and scientists who study electricity use symbols to draw electric circuits. Some of these symbols, as well as a simple parallel circuit, are shown in the diagram. Use these symbols and others found in a physical science text to make an electrical diagram of the model building. Display the electrical diagram.

Check it Out!

Conducting metals such as copper, silver, and tantalum are used to print electrical circuits on flat panels, in much the same way as words are printed in ink on the pages of this book. Find out more about printed electrical circuits. One source of information might be a television repair person. Display photographs of a circuit board with an explanation of how it was printed and what it is used for.

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From this Book:

Janice VanCleave's Electricity
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