Static Electricity: Bending and Floating

Transcription

1 Static Electricity: Bending and Floating Week 3A Objectives: In this lesson students will learn: About the force of static electricity How electricity relates to our everyday life Intro to electrons Background: How do we use electricity? Can we name some things that use electricity at home? For these experiments we will be rotating the students around the following demos that you have set up. Cotton Towel Plastic Produce Bag Scissors Balloon 1. Use a pair of scissors to cut a strip from the open end of the produce bag. Once the strip is cut, you should have a plastic band or ring. 2. Blow up a balloon to its full size and tie off the end. 3. Rub the cotton towel over the surface of the balloon for seconds. 4. Flatten the plastic band on a hard surface and gently rub the towel on the band for seconds. 5. Hold the plastic band about one foot over the balloon and release it. Static Flying Bag Rubbing the towel against the balloon and the plastic band transfers a negative charge to both objects. The band floats above the balloon because the like charges repel one another. When you rub a balloon on someone's hair the balloon picks up electrons, leaving it negatively charged and the hair positively charged. ( opposite charges attract ) Because electrical forces decrease in strength with distance, the attraction between the negatives and positives is stronger than the repulsion between the negatives and negatives. This leads to an overall attraction.

2 Questions: Do you think that the ring would have floated if you used something other than the balloon? What other materials do you think would cause static electricity other than cotton? Electromagnet Most magnets, like the ones on many refrigerators, cannot be turned off, they are called permanent magnets. Magnets like the one you are about to make that can be turned on and off, and are called ELECTROMAGNETS. They run on electricity and are only magnetic when the electricity is flowing. The electricity flowing through the wire arranges the molecules in the nail so that they are attracted to certain metals. NEVER place the wires of the electromagnet near a household outlet! Be safe have fun! Large 3 inch Iron Nail Thin Coated Copper Wire D Battery Paper Clips and Other Small Magnetic Objects Electrical Tape 1. Leave about 8 inches of wire loose at one end and wrap most of the rest of the wire around the nail. Try not to overlap the wires. 2. Cut the wire (if needed) so that there is about another 8 inches loose at the other end too. 3. Now remove about an inch of the plastic coating from both ends of the wire and attach the one wire to one end of a battery and the other wire to the other end of the battery. See picture below. (It is best to tape the wires to the battery be careful though, the wire could get very hot!) 4. Now you have an ELECTROMAGNET! Put the point of the nail near a few paper clips and it should pick them up! NOTE: Making an electromagnet uses up the battery somewhat quickly which is why the battery may get warm, so disconnect the wires when you are done exploring.

3 Questions: Does the number of times you wrap the wire around the nail affect the strength of the nail? What other objects do you think would magnetize to the nail? Salt & Pepper Experiment All matter is made up of atoms, and all atoms are made up of protons (positive charged particles), neutrons (no charge), and electrons (negative charged particles). The charges (negative and positive) are usually balanced in each atom, and so the atom is not charged. However, when you rub two things together (like a comb and hair), some electrons move from one object to the other, causing one item to have a slightly positive charge and the other to have a slightly negative charge and they now will attract each other. Combs (2) Salt and Pepper Small bowls (2) Head of hair Wool cloth (if children don t want to use hair, vice versa) 1. Place a small amount of salt and pepper in a bowl. Stir it together. 2. Have one student give a plastic comb a static charge by running it through their hair. (can use wool in place of hair) If one person charges the comb and then hands it to another person, it does not stay charged! The person who wants to do the experiment must also be the one who charges the comb! 3. Hold the statically charged comb over the dish, and the comb will attract the pepper causing it to jump up out of the dish! If you hold the comb too close, the salt will jump up too, so it might take a little practice for just the right magic effect!

4 Questions: What do you think would happen if we used different substances instead of salt and pepper? (such as sugar, other spices) What do you think would happen if the comb was metal? Electric Gelatin When you rub the balloon against the fleece or wool you charge the balloon with static electricity and when it's hovered near the gelatin, the balloon transfers the static electricity to the gelatin. Balloons Unflavored Gelatin Powder Packets Paper Plates Pieces of Wool/Fleece 1. Put paper plate out and place unflavored gelatin on plate,blow up the balloon and tie it. 2. Then rub wool on the balloon for 10 seconds or longer until you start to see the fibers of the wool standing up. 3. Then move the balloon to where the plate with the gelatin is and hold the balloon about 1 inch above the plate. 4. The gelatin will begin to react to being charged by electrons! Questions: What do you think will happen if we use other materials? (cotton,polyester, etc.) What do you think will happen if we use other items in place of the unflavored gelatin? (salt,sugar,splenda,water and cornstarch mix)

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