The Dirtmeister is your personal guide to hands-on science exploration in the classroom. By participating in Dirtmeister's Science Labs, kids have the opportunity to experience science firsthand. The steps in completing the challenge follow the same methodology used by scientists in solving problems. After reading the question, students are encouraged to formulate hypotheses. With science expert Steve Tomecek (the "Dirtmeister") serving as facilitator, students complete the hands-on investigation and check their results against their predictions.

In this Science Lab, we explore the wonderful world of circuits. Using a simple setup of batteries and bulbs, students will discover how connections in a series circuit can increase and decrease voltage. Series circuits are the simplest forms of circuits because, as the name suggests, all the components are attached in one direct line, or a series. As a result, if there are any breaks in the circuit, the whole circuit will go dead. That's because there is no alternative route for the electricity to flow. If you've ever put up those little holiday lights, you know how annoying a series circuit can be because if one bulb goes out, they all do. That means testing all the bulbs until you find the guilty culprit. On the other hand, in most buildings, if one light goes out, the rest stay on. This is because the circuit wiring is parallel, which means there is a second route for the electricity to follow.

When working with batteries and series circuits, it's very important to know the direction of the flow of electricity. Batteries produce something called direct current (DC), which means that all the electrons flow out of the negative end and return back into the positive. If two or more batteries are hooked up together in a series circuit, they have to be arranged so that the positive (+) end of one battery is touching the negative (-) end of the next. You may have noticed that if you put batteries in a radio or other portable device that uses many batteries, there is always a little chart showing which way they must go in. This is to insure that the electron flow is all in the right direction. If even one battery is turned the wrong way, the circuit won't work!

Note: The word "cell" is the proper term for a single device like a "D" or "C" cell. Batteries are devices that have more than one cell put together, like the battery in your car that usually has six cells. For simplicity, we'll just call all these devices batteries.

All batteries from the smallest button battery to the one that starts your car put out a certain amount of electricity called voltage. This number, along with the positive (+) and negative (-) ends, is printed somewhere on the battery. A typical "D" or "C" cell puts out 1.5 volts. However, when the batteries are hooked up in series, the voltage increases. In other words, two "D" cells in series give you three volts, and four cells give you six volts. As a result, when you add batteries to a series circuit with only one bulb, the bulb gets brighter because it has more electricity running through it. Of course, if you put too many batteries together, you'll burn out the bulb because the voltage will be too high! That's why every bulb has a voltage rating on it.

On the other hand, since lightbulbs use electricity, the more bulbs you hook up in a series circuit, the dimmer the light from the individual bulbs will get. Each bulb offers a certain resistance to the flow of electrons, and just like the voltage, the resistance increases as more bulbs are added. The greater the total resistance, the harder it is for the electrons to make it around the circuit, so the bulbs will be dimmer. Only when the numbers of bulbs and batteries in a series circuit are balanced will all the components work at maximum efficiency.

The Dirtmeister's Science Lab on circuits helps students meet the following science-content standards as set forth by the National Research Council of the National Academy of Sciences:

• Electricity in circuits can produce light. (Content Standard B)
• Electrical circuits require a complete loop through which an electrical current can pass. (Content Standard B)
• Electrical circuits provide a means of transferring electrical energy when heat, light, sound, and chemical changes are produced. (Content Standard B)

Classroom management is always a critical factor for any successful lesson, and the Dirtmeister's Science Lab is no exception. The following strategies will help to maximize the use of the activity in various classroom situations:

While younger students (grades 1 and 2) should have no problem making observations, they may have difficulties physically connecting the batteries and the bulbs. It may be possible to get some older "student buddies" from another class to assist with the experiment, or you as the teacher can go from station to station.

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Extensions
Here are some suggestions to enhance the experience of Dirtmeister's Science Lab for your students:

Extensions on Circuits

• Have the class try to build a super series circuit. By hooking up 30 "D" cells in series, it is possible to light a standard 25-watt 110-volt bulb. You'll need a long piece of wire for the ends. Remember, every connection must be tight. It sounds difficult, but when it works, it's GREAT!
• How much voltage does your portable "boom box" use? By counting the number of cells and adding up their voltages, students can figure out mathematically how much power they need to run a boom box. Ask the students to try this excercise with another device or toy.
• Series circuits aren't the only ways to hook up batteries and bulbs. Have the students experiment with designing and building other arrangements. See if they can make a parallel circuit with alternate routes of flow.

General Extensions

Grades K-2:

• Provide space on a classroom bulletin board for the Dirtmeister's Science Lab. Assign different teams of students the task of designing the board and changing the postings to reflect the different Science Lab topics throughout the year.

Grades 3-5:

• Using computer software such as ClarisWorks(TM) or Microsoft Works(TM), have students create and maintain electronic science journals. Encourage students to illustrate their work by using drawing or painting features of the software. This is an excellent way to keep notes and store the labs for future use.
• Have each student write an article about their favorite science experiment. Compile the articles into a science newsletter. If your class already publishes a monthly newsletter, feature a science topic in each issue, rotating the responsibility of writing the articles throughout the class.

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Resources
The following Scholastic supplemental materials can be used in conjunction with Dirtmeister's Science Lab.

• Big Books: Science (Grades K-4). This book series covers a variety of topics, from bugs to wind. They are brightly illustrated and great for the classroom library.

• Environmental Atlas of the United States, by Mark Mattson (Grade Levels 4 and up). The only environmental atlas for young readers that emphasizes U.S. ecological information.

• Be a Scientist skills books (Grades 3-6). This series includes featured scientists, hands-on activities, and an emphasis on practical process skills. The series consists of three sets of three books each for grades 3-4, 4-5, and 5-6.

• Super Science (Grades 3-6). High-interest articles and hands-on activities teach basic science and technology concepts. Each theme-based issue presents timely news and stimulates students' interest through fun activities. Exercises develop critical-thinking skills and help you meet the Natural Science Education Standards.

• Quick and Easy Learning Centers: Science, by Lynne Kepler (Grades 1-3). This Professional Resource book focuses on the use of everyday materials to promote independent, hands-on learning. Information on how-tos, management, experiments, and reproducibles are included in this helpful book.

Call Scholastic directly at 1-800-724-6527 to order and for more information.

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Related Web Sites
General Science Sites

Science and Technology for Children Curriculum
http://www.si.edu/nsrc/pubs/stc/overv.htm

The Natural History Museum (London)
http://www.nhm.ac.uk/index.html

Edison National Historic Site
http://www.nps.gov/edis/

Endangered Species Program
http://endangered.fws.gov/

National Inventors Hall of Fame
http://www.invent.org/book/index.html

Understanding Our Planet Through Chemistry
http://minerals.cr.usgs.gov/gips/aii-home.htm

Maps and References
http://www.cgrer.uiowa.edu/servers/servers_references.html

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