Lesson 4: Static Electricity

 

 

Essential Concepts:

 

Background:

·      Charge can accumulate on an object – either through a buildup of electrons (object will be negatively charged) or through removal of electrons (object is positively charged)

·      This charge accumulation – either a bunch of electrons gathered on an object or the opposite, a bunch of electrons removed from an object, is called Static Electricity

·      Remember, unlike charged objects attract each other (electrostatic attraction) ex: positive. attracts negative

·      Therefore a concentration of negatively charged particles – electrons for example – will tend to move towards a more positively or more neutrally charged object

·      An example of this is what we call a static electricity discharge– a very sudden transfer of electrons from one object to another. Ex: You build up negative charges on your body when you drag your feet on the rug, then touch a neutral object and zap- sudden discharge.

·      Another good example of static electricity is lightning. In this case there is a HUGE buildup of excess charge, which very suddenly discharges into the neutral ground. This is an example of how a large buildup of static charge can be very dangerous - you don't want it discharging through your body!

 

 

 

 

 

Goal:

Students will understand that positive and negative charges can accumulate on matter

 

 

 

Objectives:

Students will experiment with balloons, combs and static electricity

Students will continue to use the terms: “electrons”, “positive”, and “negative”

Students will observe that like charges repel one another while opposite charges attract one another

 

 

Materials:

 

Van de Graaf generator

Styrofoam peanuts

Pie plate

Plastic combs – 1 per student

Balloons – each student will need 3 with extra for damaged ones

Plastic rod 2’ x 4’ piece of wood, 24” long                      string  

Wool   Silk Cotton (note: these items should not have been in contact with any anti-static chemicals such as fabric softeners and sheets that go into the drier)

Salt      Sugar   Pepper

 

Procedure:

 

Pre class set up:

Hang the 2 x 4 piece of wood so that it is balanced and not at kid-head level. Have several balloons blown up. Set up Van de Graaf generator.

NOTE: these activities can be severely influenced by weather conditions in the classroom. They work best with cold, dry air.

 

1. Teachers may feel uncomfortable with an electrical device that plugs into the wall current and creates sparks. This is understandable. There are usually people who can be found to come in and run the Van de Graaf generator for you, should you be too unhappy with running the machine. However, if you learn from the person who is visiting and attempt to understand the way in which this machine works, you may eventually begin working with it by yourself. They are quite impressive and fun. One web site that contains many links and is also helpful is http://www.amasci.com/emotor/vdg.html (although it seems somewhat confusing at times).

            Teachers can start the class with a demonstration of how a piece of wood can be moved without any physical contact using a charged piece of plastic. Rub the plastic rod and bring it close to one end of the wood. The wood should move away from it. Try this before hand to make sure the conditions in the room are right.

2.     Now begin the demonstration of the Van de Graaf generator. Most manuals that come with the machine will suggest activities and demonstrations. Ask students what they think is happening and what it reminds them of…(lightning, static electricity, shocks from walking on a rug)

3.     Remind the students of the previous class and the discussion about atoms. What they are now seeing is an example of lots of negative electrons accumulating in one place.

4.     Students will now have the opportunity to create their own static electricity so as to complete several experiments.

5.     If you have not yet had a conversation with the students regarding the importance of communication in science, this is the time. Some might say that without proper communication, science becomes meaningless. Why might they say this? The Lab report is a wonderful and easy way to communicate ideas, experiments, results and data. The Static Electricity Exper Sheet is designed to have the students create 3 short Lab reports. Some of the information is already done for them on the sheet (For example—, hypothesis, materials) so they only have to copy that part.

6.     You may decide to give these experiments for homework or to allow them to work on them in class and at home.

 

 

 

 

Activities: discussion, demonstrations, balloon experiments, Lab Reports

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Static Electricity Experiment Sheet

 

Complete the following for each experiment:

·      Hypothesis – what is the testable question?

·      Materials – what are you using?

·      Procedure – what did you do?

·      Data & Observations – what happened? Make sure to draw a diagram and label it.

·      Conclusion – Why do you think that happened?

 

Experiment 1:

Testable Question: Can you make sugar move using only a balloon?

 

Materials: Balloon Sugar      Cloth, wool, or hair on head black construction paper

 

Extra: Try this with salt and pepper and other materials. What about rubbing things other than a balloon—try a plastic ruler. Can you make it so that the experiment does not work?

 

Experiment 2:

Testable Question: Can you make two balloons move towards one another without holding them?

 

Materials: 2 Balloons 2 pieces of String    Cloth, wool, or hair on head Stick or ruler

Procedure:

·      Blow up two balloons.

·      Tie each balloon to a piece of string and then tie the string to the middle of a stick.

·      Put the stick between two chairs so that the balloons hang down near to one another but are not touching one another.

·      ___________________________________________

 

Experiment 3:

Testable Question: Can you make two balloons move away from one another?

 

Materials: 2 Balloons String         Cloth, wool, or hair on head Stick or ruler

           Soft tip pen

Procedure:

·      Blow up two balloons.

·      Tie one balloon to a piece of string and then tie the string to the middle of a stick.

·      Put the stick between two chairs so that the balloon hangs down.

·      Use the pen to draw an “X’ on each balloon.

·      ___________________________________________

·      ___________________________________________

 

 

Extra Testable Questions: Can you make a balloon stick to a wall without tape?

                                    Can you make the water coming from a faucet bend using a plastic comb?

 

 

Remember: Sometimes you do not get the results that you expected, this does not mean that the experiment is wrong. Sometimes there are variables that can change the results of an experiment. Can you think of any variables that might change the results for these experiments?

 

 

 

** Note: all of the above should be on one worksheet —

set top and bottom margins to .5 inches **