Chapter 4-5 physical science PDF

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Christian Draper...

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Chapter 4: Electromagnetic Reactions Electricity: Benjamin Franklin:

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Determined that static electricity and lightening were different manifestations of the same phenomenon

Electric charges: 

Protons (positive), Neutrons (neutral), electrons (negative)

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Opposite charge attracts

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Same charge repels

The electric force law (coulumbs law): 

Gravity only pulls. It also works on objects with mass

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The electromagnetic force both pulls and pushes and it works on objects with charge

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F = kQq/d^2

Insulators vs. Conductors: Glass vs. Copper: 

Rubber, Glass-insulator (electrons placed on it do not move easily)

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Copper-conductor (electrons placed on it move very easily)

Electric Current: 

DC current flows one way

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AC current switches direction 60 times per second

Contact Forces: 

When two objects get close to one another, their charged parts at the surfaces repel. Also called contact force

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Not produced by some new interaction but are just another manifestation of electromagnetic interaction

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Contact force only exists when things touch

Magnetism: 

Solid metals that attract or repel one another are said to be “magnetic”

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Ferromagnetic metals (iron, nickel)

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Non-ferromagnetic metals (gold, copper, silver, etc.)

Magnetic fields: 

We can represent a magnetic field using a series of lines

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Strong field the lines are close together

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Weak field the lines are far apart

Any time you have an electric charge it creates a magnetic field

Chapter 5 Finding Forces: 

Look for forces acting on the object, not forces created by the object

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Is gravity a significant force?

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Is there a significant electromagnetic force?

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Are there significant contact forces? (friction, what is it touching)

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