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They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either...

Date post: 03-Jan-2016
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They’re Attractive & Repulsive at the Same Time
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Page 1: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

They’re Attractive & Repulsive at the Same Time

Page 2: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

When two charges are brought together they either push away from each other or they pull

towards each other.

+ +

- -

Since the charges will change their motion, Newton’s First Law tells us they must have a force applied to them!!!!

Newton’s Third Law tells us that the force on each charge must be equal in size but opposite in direction. They are an action-reaction pair!!!!

If there is no net force acting on an object, then

Page 3: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

Electric Charge

We know that there are two types of charge – positive and negative.

We know that protons are 2000 times bigger than electrons in terms of mass.

We know that even though protons are positively charged & electrons are negatively charged, protons and electrons carry the same size charge.

The size of the charge on a proton & an electron is defined in units called a Coulomb (C).

A Coulomb (C) is the unit used to measure electric charge.

Page 4: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

Electric Charge

A Coulomb of charge is very large.

It would take 6.25 X 1018 protons to make 1-C of charge.

For those of you who avoid scientific notation like the plague: It takes 6,250,000,000,000,000,000 protons to make 1-C of charge.

A proton has a charge of 1.6 X 10-19-C, an electron has a charge of -1.6X 10-19-C.

For you anti-plague people:1.6 X 10-19-C = 0.000 000 000 000 000 000 16-C

Particle

Charge (C)

Mass (kg)

Proton 1.60 x 10-19 1.673 x 10-

27

Electron -1.60 x 10-19 9.109 x 10-

31

Neutron 01.675 x 10-

27

Page 5: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

Coulomb’s LawIn 1875, Charles Coulomb did some experiments on the forces between electric charges.

He discovered two things:

1) The size of the force depends directly with the product of each charge..

FE ~ Q1∙Q2

Where Q is the size of the charge in Coulombs.

2) The size of the force depends inversely with the square of the distance between the charges.

FE ~ 1/r2

Where r is the distance between the charges.

Page 6: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

Example

Find the electrical force between a 1-C charge and a 3-C charge that are 6-m apart.

Know Formula

Work

Q1 = 1-CQ2 = 3-Cr = 6-m

The (+) answer

means the force is

repulsive – LIKE

CHARGES REPEL

Page 7: They’re Attractive & Repulsive at the Same Time. When two charges are brought together they either push away from each other or they pull towards each.

Example 2

Find the electrical force between a 5-C charge and a -5-C charge that are 100-m apart.

Know Formula

Work

Q1 = 5-CQ2 = -5-Cr = 100-m

The (-) answer

means the force is

attractive – opposite CHARGES

attract


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