1. Charge!

2. Concepts to Learn Today
Which charges attract and repel each other
Everything is electric!
Charges can be separated between two objects
Charge is always conserved

3. From the sticky tape investigation, we can conclude that there are two different types of electrical charge…

4. What are charges?
There appears to be some invisible force that sometimes attracts and sometimes repelled.
In 600 BC, the Greek mathematician Thales discovered that amber (Gk. “electron”) can attract other objects if it is rubbed with fur.
As time went on, it was discovered that electric objects can either repel or attract other electric objects.
Benjamin Franklin proposed a name for two types of electric charge: positive and negative.
Like charges repel each other; opposite charges attract.

5. What are charges?
There appears to be some invisible force that sometimes attracts and sometimes repelled.
In 600 BC, the Greek mathematician Thales discovered that amber (Gk. “electron”) can attract other objects if it is rubbed with fur.
As time went on, it was discovered that electric objects can either repel or attract other electric objects.
Benjamin Franklin proposed a name for two types of electric charge: positive and negative.
Like charges repel each other; opposite charges attract.

6. We know today that these “electric” charges come from atoms—which are made of tiny electric charges called protons and electrons!

7. So, because everything is made of atoms, all matter is electric in nature! Stones, stars, and all living things—all stuff is made up of atoms, which are made up of electric charges!
We know today that these “electric” charges come from atoms—which are made of tiny electric charges called protons and electrons!

8. How important are electric charges?
Charges are everywhere and mean everything to how our world is structured.
Charges provide:
Strong chemical bonds like in NaCl (salt)
The tension force in a stretched spring
The adhesive force of glue
The normal force between your butt and the chair
Can you think of an example of charges at work in your life?

9. There’s no skiing without charges!

10. What does it mean to be electrically charged?
J.J. Thomson discovered that electric charge comes in a natural unit, with a proton and electron representing the smallest amount of charge.
Proton = positive charge Electron = negative charge
If an object has an excess of protons or electrons, it is said to be charged (either positively or negatively).
Neutral objects have equal amounts of positive and negative charges.

11. What does it mean to be electrically charged?
Neutral
J.J. Thomson discovered that electric charge comes in a natural unit, with a proton and electron representing the smallest amount of charge.
Proton = positive charge Electron = negative charge
If an object has an excess of protons or electrons, it is said to be charged (either positively or negatively).
Neutral objects have equal amounts of positive and negative charges.

12. Charge is made up of natural units or discrete amounts, similar to our money system.
Cash is in one-cent increments. You cannot divide a large amount of cash into an amount smaller than one cent.
Similarly, charge is in increments. The proton and electron have the smallest charge possible, and all charge is measured in increments of this “fundamental” charge.

13. Charge is “Conserved”
You may have experienced the consequences of separating charges already… ation/john-travoltage

14. Charge is “Conserved”
Charges are separated and transferred between objects, but the total amount of charge in the system remains the same.
If your socks pull 100 electrons off the carpet, let’s say your socks acquired a charge of -100.
What’s the total charge on the carpet?
What’s the total charge of the system?

15. Charge is “Conserved”
Charges are separated and transferred between objects, but the total amount of charge in the system remains the same.
If your socks pull 100 electrons off the carpet, let’s say your socks acquired a charge of -100.
What’s the total charge on the carpet?
What’s the total charge of the system?
Charge cannot be created or destroyed—you never lose charge. In other words, charge always goes somewhere!

16. Charge is “Conserved”
Carpet fibers on a dry day are good insulators. Why? Rubbing causes charge to build up on you, and—since it can’t flow through the insulating fibers of the carpet—it remains on you! That is, until you touch a conducting doorknob!
You may have experienced the consequences of separating charges already… ation/john-travoltage

17. Charge is “Conserved”
Anytime electrons are transferred from one object to another, the total electric charge in the whole system remains the same.
If an object gains electrons, it acquires a negative charge.*
If an object loses electrons, it acquires a positive charge.*
If you rub a neutral plastic rod and fur together, the rod acquires a negative charge (by taking electrons) but the fur acquires a positive charge of the same magnitude (since it lost as many electrons that the rod gained).
*Notice that only electrons are the charges that get transferred between objects, never protons. We’ll see this more tomorrow!

18. When the upper and lower pieces of tape were pulled apart, what conclusions can you make about the electric charges?
Answer this question on the back of the sticky tape Experiments paper

19. Exit Quiz
What happens when two materials with the same charge are brought near each other?
What are the two kinds of charges called?
What kind of charge does a proton possess?
Why do we say everything is electric?
If the “upper” piece of tape acquired 100 electrons and acquired a charge of -100 as it was ripped off the “lower” piece of tape. What must the charge on the “lower” piece of tape be?