Electrostatics

3 Big Ideas What are the three basic types of particles you find in a neutral atom? What are the three basic types of particles you find in a neutral atom? –What are their similarities and differences? How do these particles behave when they are in the presence of another? How do these particles behave when they are in the presence of another? How do the charges move and why do they move? How do the charges move and why do they move?

Big Idea # 1 Three Types of Charges Three Types of Charges –Protons, Electron & Neutron Only the negative charges (electrons) move Only the negative charges (electrons) move The positive charges (protons) are stationary The positive charges (protons) are stationary So are the neutral charges (neutrons) So are the neutral charges (neutrons)

Big Idea # 2 Like charges… Like charges… –repel Opposite charges… Opposite charges… –attract Basically… If two objects have the same charge they push each other away, but if they have opposite charges, they attract each other.

Big Idea # 2 If they push or pull each other then they must apply a… If they push or pull each other then they must apply a… –FORCE! –Electrostatic Force k is a constant: 9x10 9 Nm 2 /C 2 k is a constant: 9x10 9 Nm 2 /C 2 The q’s are the quantity of charge measured in Coulombs (C) The q’s are the quantity of charge measured in Coulombs (C) The d is the distance between the 2 objects in meters The d is the distance between the 2 objects in meters When you calculate F e When you calculate F e –This is how much q a pulls or pushes on q b or… –How much q b pushes or pulls on q a –It’s how much the push or pull on each other! –(Newton’s 3 rd Law!)

Big Idea # 3 Electrons will move from a high concentration to a low concentration until there are equal amounts everywhere Electrons will move from a high concentration to a low concentration until there are equal amounts everywhere The negative charges flow The negative charges flow from a large amount to an area where the number of electrons are lower. Why? Why? –Like charges repel –Coulomb’s Law

Charge on an object Most objects start off neutral Most objects start off neutral –Which means they have equal +’s as –’s. If an object looses electrons (-)… If an object looses electrons (-)… –Then the object is charged positive. If an object gains electrons (-)… If an object gains electrons (-)… –Then the object is charged negative.

Conservation of Charge When charges transfer, the total charge (net charge) remains the same. When charges transfer, the total charge (net charge) remains the same. If the charge on A is - 4, and the charge on B is - 6, what charge would each have after they are connected and charges are allowed to flow? If the charge on A is - 4, and the charge on B is - 6, what charge would each have after they are connected and charges are allowed to flow? AB

Conservation of Charge Answer: Each would have a -5 charge. Answer: Each would have a -5 charge. Total charge (net charge) before = -10 Total charge (net charge) before = -10 – -10 = (- 4) + (- 6) –The charges flow from high to low until they are EQUAL –So each would get a – 5 charge.  (- 10 / 2) = - 5

Conservation of Charge The charge on A is - 9, the charge on B is - 3, and the charge on C is + 4. The charge on A is - 9, the charge on B is - 3, and the charge on C is + 4. What charge would each have after A touches B, they are separated and then B touches C? What charge would each have after A touches B, they are separated and then B touches C? ABC

Conservation of Charge Answer: Answer: –A = -6 –B = -1 –C = -1 Net charge (A & B) before = -12 = (-3) + (-9) Net charge (A & B) before = -12 = (-3) + (-9) –Each gets a (- 6) charge = (- 12 / 2) Net charge (B & C) before = -2 = (-6) + (+4) Net charge (B & C) before = -2 = (-6) + (+4) –Each gets a (- 1) charge = (- 2 / 2)

Types of materials Conductor- Conductor- –Allows electrons to flow thru easily (very little resistance). –Resistance is like friction.  Ex. Metals, water –These are on the left side of the zig-zag line on the periodic table

Types of Materials Insulator- Insulator- –Does not allow electrons to flow thru easily  But they can still go thru –Ex. Wood, plastic, air, rubber, glass,… –These are located on the right hand side of the zig-zag line on the periodic table.

Types of Materials Semi-Conductor- Semi-Conductor- –A material that is sometimes conductor, sometimes an insulator –Depends on what the temperature  Ex. Silicon, Polonium,… –These are the elements that are touching the zig-zag line on the periodic tabe (metalloids)

Types of Materials Super Conductor- Super Conductor- –These are materials that are conductors with zero resistance. –Kind of like a frictionless surface. –This only occurs at extremely cold temperatures (liquid nitrogen cold)

Homework FUN! Packet Packet –Worksheet 1