For the part about making a battery, you need lemons, pennies, wire, and galvanized nails (easily found at any hardware store - often called "roofing" nails, they are coated in zinc; but  I provided some zinc strips already to you at our last lab.)  You can also make the vinegar battery as well with some standard vinegar found at any grocery store.  This part is a bit more involved, but not that much.  If you have a flashlight you can borrow the bulb from it to test your battery, or try the calculator method in the video.  We'll continue this lab at our next on-campus meetings, Wednesday 10/8 or Thursday 10/9.

Home Lab #2 Part 1: Static Electricity

Home Lab #2 Part 2: Making a Battery Videos

Static Electricity 

The purpose of this activity is to study different charge interactions between objects and to draw some generalizations about the attractive and repulsive nature of these interactions. 
Please answer the following questions carefully, labeling your answers clearly with the question involved. This section could take 1-2 hours. If you would like schematics of how to create
the sticky tapes for this section, check out:

Doherty, Paul. (2000, May 30) Explore static electricity with sticky tape http://www.exo.net/~pauld/summer_institute/summer_day14electrostatic/tape_electroscope.html

Paul Doherty is a world-reknown scientist and educator who works for the Exploratorium in San Francisco; backtracking to his site you might find some wonderful additional resources.

Part A: Electrical Interactions

A1.  Tear part of a piece of paper into very small bits (about the size of confetti, no more than a few millimeters wide.. Take a plastic pen and bring it close to the bits of paper.
Can you lift the bits of paper by touching them with the pen?

A2.  Now rub the pen briskly against your hair (or a wool sweater) and try to lift the bits of paper from the table. Can the scraps of paper be lifted even if you do not allow the
rubbed pen to touch them first?

A3.     Repeat this using a Styrofoam coffee cup, trying to lift the paper bits before and after rubbing the cup on wool or your hair. What are your results with the cup?

A4.     Apparently, after the pen has been rubbed there is an interaction between the pen and paper which is capable of lifting the scraps of paper. What can you say about the size
(smaller, larger, or the same size) of this interaction force compared to that of the earth's gravitational interaction force with the scraps of paper? Explain.

A5.     DEFINITION: The force involved in this interaction is called an electrical force, and was first observed by the Greeks, who found that pieces of amber (in Greek, “elektron”) attracted other things after being rubbed with fur. Materials which are capable of attracting the bits of paper are said to be electrically charged.

A6.     Is the Styrofoam cup electrically charged according to the definition given in #5? ______ Explain.

A7.     Are the bits of paper charged according to the definition given in #5? ______

A8.  Devise and perform a mini-experiment to determine whether the paper is charged. Describe the procedure of your mini-experiment.   Are the paper bits charged?
Explain your answer with support from your mini-experiment.

Part B: Interaction Between Charged and Uncharged Objects 

B1.   Obtain about 15 cm of the Scotch tape and make tabs by folding the first centimeter of tape on each end, sticky side together. Stick the tape to the table-top and press and

rub it down well with your finger. Now peel the tape carefully but briskly from the table top.

B2.   Will either or both sides of the tape attract the scraps of paper? __________ Explain what happens.

B3.   Does the tape meet the definition of being charged (see definition in Part A)? __________ Explain.

B4.   Roll a piece of paper into a tube and bring it near the tape. Is there an interaction between the paper and the tape? _________ What type of interaction (attractive or repulsive) is it?
 

B5.   In Part A, a definition was given for an object being charged. Does the paper tube meet your definition of being charged? ________ Explain why or why not.

B6.   Make a second tape strip like the first one. Press them both down on the table separately, and then peel them loose from the table. Try bringing the tapes near each other.
What effect (attract, repel or no interaction) do they have on each other? ____________________ Does it matter which sides of the tape face each other?

B7.   Make a third strip of tape, charge it and try bringing it close to each of the other two tapes. Compare one of yours with those of another student, or stick their ends to something
so that you have enough hands. What do you observe?

B8.   REVISED DEFINITION: In Part A, a definition was given for an object being charged. Here we have found that the definition is not quite complete. Based on these observations, extend your definition of an object which is electrically charged.

Part C: Do All Charged Objects Behave the Same Way?

C1.   Tape a plastic pen to the top of your desk or table so that about three-fourths of the pen sticks out over the floor.

C2.   Charge another 15-cm tape by sticking it to the table top, rubbing the tape, and peeling the tape from the table. Hang this charged tape from the end of the pen by sticking
the tape to the pen. This is a test tape.

C3.   Make two new tape strips in the following manner. Label the first one A, press it down on the table, and rub it with your finger. Label the second one B, press it firmly down
on top of A, and rub it with your finger. Peel the two-tape combination off the table. (They will be stuck together!) Bring them near the test tape. What do you observe?

C4.   Bring the combination near some paper bits. What do you observe (attraction, repulsion or no interaction)?

Is the combination tape charged under either or both parts of your definition? Explain.

C5.   Carefully peel apart the two tapes. Hold one in each hand and bring them slowly towards each other.

C6.   Bring A towards the test tape.  What do you observe (attraction, repulsion or no interaction)?

      Bring B toward the test tape. What do you observe (attraction, repulsion or no interaction)?

C7.   Are both A and B charged according to your definition of charged? ___________ Explain why or why not.

C8.   Devise a mini-experiment that will show convincingly that both A and B are charged according to your definition. Write down the steps of your mini-experiment and try it.

C9.   How does testing for charge by attraction compare to testing by repulsion in terms of their relative effectiveness as a test for an object being charged?  Would either test alone be sufficient? ______ If so, which one and explain why. If not, explain why not. (This is an important question!)

C10. REVISED DEFINITION: The definition for an object being charged was last revised in Part B. You now need a new definition for an object being charged. Revise your old definition.

 C11. Tape another pen to your desktop with three-fourths of the pen hanging over the floor like you did in #1. Hang tape A on the end of one pen and tape B on the end of the other pen. Try rubbing various objects including a pen and a foam cup against various materials and test them against tapes A and B. Conduct a sufficient number of tests in order to answer the following questions. Record your observations!

C12. Do all objects that repel A also attract B? __________ Do all objects that repel B also attract A? __________ Do any objects repel both A and B?  __________
Do any objects attract both A and B? __________ Do these objects meet your definition of being charged? __________ Explain how you know.

Part D: Charges and Charged States

IMPORTANT: If two charged objects behave the same in their interactions with all other objects, we may describe them as being in the same charged condition or in the same charged state. We will suppose that a charged state depends on the presence of something called charge. With this hypothesis, we need to account for the charged states of A tapes, B tapes, and unrubbed paper in terms of the kind or kinds of charges present.

D1.  How do two A tapes interact (attract, repel or no interaction)? __________ How do two B tapes interact (attract, repel or no interaction)? _________

D2.   Based on your experiences would you say that the two A tapes have the same or different charge? _____________ Would you say that the two B tapes have the same or different charge? ________________

D3.   On the basis of these observations we now assume that A tapes have one kind of charge and B tapes have another. What is the interaction (attract, repel or no interaction) between two objects with the same kind of charge?

D4.   How does an A tape interact (attract, repel or no interaction) with a B tape? ________ Describe the interaction between two objects with different kinds of charge.

D5.   How do two bits of unrubbed paper interact?_________ If we were to assume that the behavior of unrubbed paper is due to the presence of a third charge, would the behavior
of this third charge be consistent with the behavior of A and B? _________ Explain your answer.

D6.   How does an A tape interact (attract, repel or no interaction) with a B tape?

D7.   How does an A tape interact (attract, repel or no interaction) with paper bits?

D8.   How does a B tape interact (attract, repel or no interaction) with paper bits?

 Conclusion:

1.   Use complete and detailed sentences to describe the different types of interactions (attractive, repulsive or no interaction) which exist between positively charged, negatively charged, and neutral objects.

2.   Describe what definitive observation (or set of observations) which would have to be made in order to determine whether or not an object is charged.

 Please carefully record your answers to each of these questions as well as all your data (answering questions in each section A through D).  This should be turned in (or emailed me)
when you next come on campus 10/8 or 10/9.

Making a Battery

1. Observe the short video about a vinegar battery (http://video.google.com/videoplay?docid=4850277179425254045&hl=en ) 

2. Observe the second short video about a lemon battery  (http://video.google.com/videoplay?docid=-6226504780579469841 )

3  POST in our lab discussion area your thoughts about how these videos.  Do they help you to understand electricity?  Add as well a brief summary of what you learned from the first part of the lab in general, with sticky tapes!
 

Optional: Make your own Battery!

This is not required, but it is fun.  If you don't have a convenient bulb from a flashlight, you can try the calculator method if you have a spare old battery-powered model.  But you do need to bring your battery to class for the next week's on-campus lab for credit here!  We'll use our physics equipment there to measure voltages and current and see what we can power.