1. Electric Charge

2. Remember the tipsy tape pieces?
What happened when both pieces of tape were stuck to the same surface then brought close to each other?
the tape pieces moved away from
each other.
What is the scientific word for this action?
repel – write this in your notebook

3. Remember the moving tape pieces?
What happened when one piece of tape was stuck to the table then the other piece of tape was stuck on top?
the tape pieces moved toward
each other.
What is the scientific word for this action?
attract– write this in your notebook

4. Review from the Motion and Forces Unit…
What type of force must be happening between the tape pieces to make them move – balanced or unbalanced? An unbalanced force must be between the tape pieces.

5. What the heck?!
What you created with the straws and tape is an “electroscope” – a device that detects electrical charge. An electroscope used in a testing lab might look like this:

6. How does an electroscope work?
When the little metal leaves inside the glass both have the same electric charge, they repel each other and move apart. When the leaves have opposite charges they attract and move back toward each other.

7. What’s going on with the tape?
When you rip a piece of tape off the table, there is a tug-of-war for electric charges between tape and table. The tape either steals negative charges (electrons) from the surface or leaves some of its own negative charges behind, depending on what the surface is made of.

8. Understanding tape atoms
By the way, which subatomic particle inside of an atom has a negative charge? Can you remember from Elementary School? an electron has a negative charge (write this down)

9. Understanding tape atoms
It is always the electrons that jump from one object to another, because protons and neutrons are much too big to move. What charge do protons have? Positive (write this down) What charge do neutrons have? No charge (write this down)

10. What’s going on with the tape?
Back to the whacky tape… When you pull two pieces of tape off the same surface, both pieces of tape end up with the same kind of charge. What evidence do we have that the pieces of tape are the same charge? Since the tape pieces repelled each other, this is evidence that they have the same charge.

11. What’s going on with the tape?
When the tape sandwich is pulled apart, one piece rips electrons away from the other. The piece that gained electrons now becomes negatively charged. The piece that lost electrons now becomes positively charged. Since opposite charges attract, the two pieces of tape move toward each other.

12. What’s going on with the comb?
When you rub a comb on wool (or any type of hair) the comb grabs extra electrons from the hair and becomes negatively charged.
In your notebook, draw a picture of the comb and what is going on with the electrons.

13. What’s going on with the comb?
If a piece of tape is repelled by the comb, the tape must have the same charge as the comb. (they are both negative) If a piece of tape is attracted to the comb, the tape must have the opposite, positive charge. (since the comb has a negative charge)

14. Re-Create this in your notebook.
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
_______
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
Attracted to tape C. Attracted to comb.
Tape - Plastic
_____________ by comb.
Tape - Aluminum
Tape - Cotton

15. If tape A is repelled by the negative comb…
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
_______
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
Attracted to tape C. Attracted to comb.
Tape - Plastic
_____________ by comb.
Tape - Aluminum
Tape - Cotton

16. If tape B is repelled by the negative comb…
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
_______
Attracted to tape D. Repelled by comb.
Tape D
Attracted to tape C. Attracted to comb.
Tape - Plastic
_____________ by comb.
Tape - Aluminum
Tape - Cotton

17. If tape C is repelled by the negative comb…
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
_______
Attracted to tape C. Attracted to comb.
Tape - Plastic
_____________ by comb.
Tape - Aluminum
Tape - Cotton

18. If tape D is attracted to the negative comb…
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
positive
Attracted to tape C. Attracted to comb.
Tape - Plastic
_______
_____________ by comb.
Tape - Aluminum
Tape - Cotton

19. Fill in the last 3 lines from yesterday’s observations
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
positive
Attracted to tape C. Attracted to comb.
Tape - Plastic
_______
_____________ by comb.
Tape - Aluminum
Tape - Cotton

20. Did yours react the same as mine? Infer?
Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
positive
Attracted to tape C. Attracted to comb.
Tape - Plastic
_______
Attracted by comb.
Tape - Aluminum
Repelled by comb.
Tape - Cotton

21. Object
Charge
Evidence / Observations
Plastic Comb
Negative
Tape A
negative
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
positive
Attracted to tape C. Attracted to comb.
Tape - Plastic
Attracted by comb.
Tape - Aluminum
Repelled by comb.
Tape - Cotton

22. What type of observations are these?
Object
Evidence / Observations
Tape A
Repelled by tape B. Repelled by comb.
Tape B
Repelled by tape A. Repelled by comb.
Tape C
Attracted to tape D. Repelled by comb.
Tape D
Attracted to tape C. Attracted to comb.
Qualitative

23. Materials act differently… (hint: there will be this type of chart on the test)
If you rubbed silk fabric onto a rubber stopper, what charge would you expect the silk to have? silk = lose electrons = positive What charge would you expect the rubber stopper to have? rubber = gain electrons = negative

24. Notice that the attraction or repulsion happens without the objects touching…
The balloon can attract or repel without touching each other. Same as the comb and the tape.
Electric forces can act “at a distance”.
(write this down)
These balloons are both negatively charged, so they repel each other even though they don’t touch.

25. Now test your understanding, while standing
If the response is positive, cross your arms to form a plus sign
If the response is negative, place your arms on top of each other to form a minus sign.
If the response is neutral, place your arms to your sides, to indicate nothing.

26. Stand on your chairs – ready go!
An atom gains extra electrons so it is now _____________ charged. An atom is just chillin’ so it is ________________. An atom loses electrons so it is now _______________ charged. A object is attracted by a negatively charged comb, so it must be ____________ charged. An object is repelled by a positively charged piece of fur, so it must be ____________ charged. An atom is part of a human resting in bed, so it is probably _________. An atom is part of a human who has rubbed her feet on the carpet, so now it has gained electrons and become __________ charged.

27. A quick summary – (draw this model in your notes)
Two opposite charges will attract
Two positive charges will repel
Two negative charges will repel
The force of attraction or repulsion between charged particles is called ELECTRIC FORCE