It s Shocking! Static Electricity Experiments

Transcription

1 Static Electricity Experiments Synopsis The purpose of this inquiry-based lab/lesson is to have students conduct several experiments to learn about static electricity. Background From this lab, students should develop an understanding that charged objects create an invisible electric force field around themselves. The strength of this field depends on many things, including the amount of charge, distance involved, and shape of the objects. Specifically, they should know that the greater the charges, the stronger the force field and the greater the distance, the weaker the force the force field. Static electricity is the imbalance of positive and negative charges. The students should understand that there are two kinds of electrical conditions called plus and minus but at this level, they do not need to have understanding of atoms, electrons, and protons. Usually, items are neutral but rubbing two things together can cause one item to have a plus charge and the other to have a minus charge. An object that is charged has an electric force field coming from the surface. This field will mildly attract neutral objects and will strongly attract an object that has an opposite charge on its surface. If two objects have the same charge, the electrical force field will cause those objects to push away from each other. A reference can be made to the north and south poles of magnets if the students have experience with magnets. If two objects of the same material are treated in the same way (e.g. two balloons rubbed with wool), they will have the same charges and will repel each other. Only if they are treated differently will they attract each other. A charged object will also attract something that is neutral. When you stick a balloon to a wall, you charge the balloon by rubbing it on your hair, which causes the balloon to pick up extra electrons giving it a negative charge. Holding near a neutral object will make the charges in that wall move and the negative charges in the wall move as from the balloon as possible. This makes more positive charges close to the negative balloon at the balloon will stick until the electrons slowly leak off. After rubbing the balloon on your hair, your hair sticks up because the individual hairs lost electrons, are now all positively charged and since things with the same charge repel each other, they try to get as far away from each other as possible. When you walk across a rug, electrons move from the rug to you. When you touch a doorknob or something else, the electrons move from you to the knob and you get a shock because they are discharged so quickly.

2 Objectives 1. Students will conduct 4 experiments to learn about static electricity. 2. Students will become more familiar with the scientific method. 3. Students will develop writing skills by completing the required sections for each experiment. 4. Students will develop inquiry skills by developing their own testable question and experiment. Suggested Timeline Day one. Student experiments. 50 min. Day two. Discussion of experiments and presentation of important points. 20 min. Materials (for each group) Balloons (one loose, one on a string approx 1-1.5m long) Empty soda can Confetti (or very small pieces of paper) Plastic grocery bags (2) Wool fabric (2 pieces) Plastic Comb Salt and Pepper (one small restaurant package per group or use shakers for the entire class) Teaching Tips Warm-up: (use any or all) 1. Have you ever been shocked after walking on a rug or putting on a sweater? What do you think caused the shock? 2. Why do you think clothes stick together when they come out of the dryer? 3. What other experiences have you had with static electricity? Introduce the lab by saying that they will be conducting some experiments to learn more about static electricity and electric charges. Explain that for each experiment, they will need to complete the seven sections that are each part of the scientific method. For some of the experiments, sections have been completed for them.

3 Static Electricity Experiments Have you ever been shocked after you walked across a rug? Have you seen clothes stick to each other after you remove them from the dryer? Have you stuck a balloon to a wall after rubbing it on your hair? All of these things have to do with static electricity but what is it and how does it happen? Complete the following for each experiment: Question- what is the testable question? Observations- what are two observations about the materials? Hypothesis- what is your prediction? Materials- what did you use? Procedure- what did you do? Data- what happened? Draw a diagram and label it. Conclusion- why/how do you think that happened? Available Materials Balloons (one loose, one on a string) Empty soda can Confetti Plastic bag Wool fabric Comb String Water Faucet cereal (Cheerios, puffed rice, etc) Salt Pepper Flour Sugar

4 Experiment 1 Testable Question: Can you use a balloon or a comb to pick up confetti? Observations: (Record two observations of your own.) 1. The balloon is rubbery. 2. The confetti is really small Hypothesis: (Do you agree with the below hypothesis? If not formulate your own.) The wool fabric will make the confetti stick to the balloon. Yes or No Balloon or Comb Wool fabric Confetti 1. Sprinkle the confetti onto the table. 2. Rub the comb or one side of the balloon with the wool fabric. 3. Bring the comb or that side of the balloon down toward the confetti but do not touch any of the pieces of paper.

5 Experiment 2 Testable Question: Can you make two balloons repel (move away from) each other? Observations: Hypothesis: Balloons (one loose, one on a string) Wool fabric 1. Have one person hold the string tied to one balloon at arms length. 2. Rub that balloon with the wool fabric. 3. Rub the other balloon with the same wool fabric. 4. Bring the loose balloon close to the balloon on the string.

6 Experiment 3 Testable Question: Can you make a balloon or comb attract (move towards) water? Observations: Hypothesis: Balloons (one loose, one on a string) Wool fabric Plastic bag 1. Turn on the faucet so that the water runs out in a small, steady stream, about 1/8 inch thick. 2. Charge the comb by running it through long, dry hair several times or rub it vigorously on a sweater. 3. Slowly bring the comb near the water and watch the water "bend." 4. Now repeat steps 1-3 using a charged balloon. (balloon rubbed with the wool)

7 Experiment 4 Testable Question: Can you make a piece of cereal move without touching it? Observations: Hypothesis: 1. Tie a piece of the cereal to one end of a 12 inch piece of thread. Find a place to attach the other end so that the cereal does not hang close to anything else. (You can tape the thread to the edge of a table but check with your parents first.) 2. Wash the comb to remove any oils and dry it well. 3. Charge the comb by running it through long, dry hair several times, or vigorously rub the comb on a wool sweater. 4. Slowly bring the comb near the cereal. It will swing to touch the comb. Hold it still until the cereal jumps away by itself. 5. Now try to touch the comb to the cereal again. It will move away as the comb approaches.

8 Experiment 5 Testable Question: Observations: Hypothesis: