Static Electricity and Separation of Electric Charge

2. “Static” Electricity Separation of Electric Charge

3. Prepare three 4 to 6-inch long pieces of invisible tape. Fold one end of each tape under to make a non-sticky handle.

4. Stick the first strip of tape to a smooth, flat surface, such as your desktop. This is your “base” tape. Use it as the base tape for each procedure that follows. Smooth this tape down with your thumb or finger.

5. Stick a second tape down on top of your base tape, and smooth it down well with your thumb or finger. Write “U” (for upper) on the handle of this tape.

6. With a quick motion, pull the U tape off of the base tape, leaving the base tape stuck to the table.

7. Hold the U tape or hang it from the desk. Bring your hand slowly towards the hanging tape. What happens? Pulling the U tape away from the base tape alters the U tape so that it is attracted to other objects. We say that such a tape has been “charged” or “electrified” and you should handle electrified tapes by their ends.

8. Predict what will happen if 2 U tapes are brought together.

9. Predict what will happen if 2 U tapes are brought together. Make a second U tape and bring it near the first.

11. Put a tape with a handle on the base tape as before, but write “L” (for lower) on its handle. Next put a U tape on top of the L tape. You now have three layers of tape, a base tape, an L tape, and a U tape.

12. Smooth the upper tape with your thumb or finger as before, then lift the L tape off of the base tape, so that the U tape comes off as well. Rub your thumb or finger along the smooth side. This should eliminate the attractive interaction.

13. Make a second L - U tape combination. Rub your thumb or finger along the smooth side. This should eliminate the attractive interaction.

14. Make predictions.

15. After verifying that the pair of tapes is no longer attracted to other things, quickly separate the pair of tapes.

16. Do experiments to test your predictions.

18. What's going on here? Figure out an explanation for the behavior of U and L tapes and then write it.

19. Your explanation should account for: The interaction of U tapes with each other. The interaction of L tapes with each other. The interaction between U and L tapes. Be sure to support your conclusions with evidence (experimental observations).

21. Pieces of “electrified” tape exert forces on each other. We call these forces, Electric Forces Electric forces can attract or repel. This is different from gravity which only attracts.

22. What produces electric forces?

23. Electric Charge There are two kinds of charge in nature. Negative Positive Images courtesy of Particle Data Group of Lawrence Berkeley National Laboratory.

24. Electric Charge The names of “positive” and “negative” for the two types of charge come from Benjamin Franklin.

25. Electric Forces Electric charges exert forces on each other. “likes” repel opposites attract Electric Forces between two objects are stronger when the objects are close to each other and weaker when they are farther apart. Images courtesy of Particle Data Group of Lawrence Berkeley National Laboratory.

26. How do the strips of tape become electrified?

27. Electric Charge Under most conditions, matter has equal amounts of positive and negative charge. Negative Positive Images courtesy of Particle Data Group of Lawrence Berkeley National Laboratory.

28. Static Electricity Static electricity results from the separation of positive and negative charges. + ¯ + ¯ + + + ¯ ¯ + ¯ ¯ + + + ¯ ¯ ¯ + ¯ When two dissimilar objects touch, particles with electric charge are transferred from one object to the other.

29. Static Electricity Static electricity results from the separation of positive and negative charges. + ¯ + ¯ + + + ¯ ¯ + ¯ ¯ + + + ¯ ¯ ¯ + ¯ More negative charges than positive charges. More positive charges than negative charges.

30. Static Electricity Static electricity results from the separation of positive and negative charges. • When two dissimilar objects touch, particles with electric charge are transferred from one object to the other. • One object ends up with more particles that have a negative charge than particles with a positive charge, so we say it has a net negative charge. • The other object ends up with more particles that have a positive charge than particles with a negative charge, so we say it has a net positive charge.

32. Static Electricity Why are electrified objects attracted to other objects? ¯ Matter is made up of particles that have a positive charge (protons) and particles that have a negative charge (electrons). + + ¯ ¯ +

33. Static Electricity Why are electrified objects attracted to other objects? When an object with an excess of positive or negative charge is brought near another object, how will the charge on the object interact with the atom’s protons? . . . electrons? ¯ ¯ + ¯ ¯ ¯ ? ¯ + ¯ ¯ ¯ ¯ ¯ ¯ ¯ + ¯ ¯

34. Static Electricity Why are electrified objects attracted to other objects? When an object with an excess of positive or negative charge is brought near another object, attraction and repulsion cause a small shift of the charges within the object. ¯ ¯ + ¯ ¯ ¯ ¯ + ¯ ¯ ¯ ¯ ¯ ¯ ¯ + ¯ ¯

35. Static Electricity Why are electrified objects attracted to other objects? Opposite charges are now slightly closer to each other than like charges. So, attraction between the objects is stronger than repulsion between them and they attract. ¯ ¯ + ¯ ¯ ¯ ¯ + ¯ ¯ ¯ ¯ ¯ ¯ ¯ + ¯ ¯