Electrostatics

3 Big Ideas

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 the charges move and why

do they move?

Big Idea # 1

Three Types of Charges– Protons, Electron &

Neutron Only the negative

charges (electrons) move

The positive charges (protons) are stationary

So are the neutral charges (neutrons)

Big Idea # 2

Like charges…– repel

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…– FORCE!– Electrostatic Force

k is a constant: 9x109 Nm2/C2

The q’s are the quantity of charge measured in Coulombs (C)

The d is the distance between the 2 objects in meters When you calculate Fe

– This is how much qa pulls or pushes on qb or…– How much qb pushes or pulls on qa

– It’s how much the push or pull on each other! – (Newton’s 3rd Law!)

𝐹𝑒=𝑘𝑞1𝑞2𝑑2

Big Idea # 3

Electrons will move from a high concentration to a low concentration until there are equal amounts everywhere

The negative charges flow from a large amount to an area where the numberof electrons are lower.

Why?– Like charges repel– Coulomb’s Law

Charge on an object Most objects start off neutral

– Which means they have equal +’s as –’s. If an object looses electrons (-)…

– Then the object is charged positive. 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.

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?

A B

Conservation of Charge

Answer: Each would have a -5 charge.

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.

What charge would each have after A touches B, they are separated and then B touches C?

A B

C

Conservation of Charge

Answer:– A = -6– B = -1– C = -1

Net charge (A & B) before = -12 = (-3) + (-9)– Each gets a (- 6) charge = (- 12 / 2)

Net charge (B & C) before = -2 = (-6) + (+4)– Each gets a (- 1) charge = (- 2 / 2)

Types of materials

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- –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- – 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- – 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 –Worksheet 1