Chapter 15 Outline Honors Physics

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Chapter 15 OutlineHonors Physics

• Created for CVCA Physics
• By
• Dick Heckathorn
• 24 February 2K 5

2
Father of Electricity

• Ben Franklin
• positive charge
• charge on glass rubbed by silk
• negative charge
• charge on ebony rubbed by fur

3
Law of Electric Charges

• Opposite electric charges attract each other.
• 2. Similar electric charges repel each other.
• 3. Charged objects attract some neutral objects.

4
Structure of Matter

• 1. All matter composed of atoms.
• 2. Electric charges carried by
• electrons and protons
• 3. Elementary Charge charge of electron and
  proton.
• 4. Neutrons no electrical charge
• 5. Are both negative positive ions

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Charge Movement

• 1. Positive charge proton, is located in the
  nucleus, thus not free to move.
• 2. Negative charge electron, free to move
• 3. Therefore, all excess in charges in solids
  result either from an excess or deficit of
  electrons.

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Broad categories of substances

• Conductor electrons are able to move freely
  from one atom to another in a solid.
• Insulator electrons are not free to easily move
  from one atom to another in a solid.
• Liquids gases - can move

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Convention

• 1. Charged objects marked with - have an
  excessive of electrons.
• 2. Charged objects marked with have a
  deficiency of electrons.
• 3. Number of - or signs do not represent
  the actual number of
• - or charges on the object.

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Convention

• 1. Charged objects marked with - have an
  excessive of electrons.
• 2. Charged objects marked with have a
  deficiency of electrons.
• 3. Number of - or signs do not represent
  the actual number of
• - or charges on the object.

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Convention

• 4. Neutral objects are not marked with equal
  number of - or signs but are shown with no
  - or signs.
• This does not agree with what your text does in
  some situations.

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Charging by Friction

• 1. There is a transfer of electron from one
  object to the other according to how tightly each
  are held to the positive charges in their nucleus.

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Electrostatic Series

• Add from other power point

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Induced Charge Separation

• a. Rub white rod with wool
• b. With sphere near the white rod, touch sphere
  with finger making sure the sphere does not touch
  the white rod.
• c. Check charge using the electroscope.

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Induced Charge Separation
Touch with finger.
Remove finger.
Remove rod.
Bring sphere near negative strip.
Electrons move to opposite side.
Positive charges remain near rod.
Electrons escape from sphere
Induction Explanation
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Induced Charge Separation

• 1. Charges are rearranged on an object (A) by the
  presence of another charged object (B).
• 2. Touching object (A) will allow electrons to
  flow onto or off it.
• 3. The charge on object (A) will always be
  opposite the charge on object (B).

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Charging by Contact

• a. Rub white rod with wool
• b. Touch sphere to white rod until it repels.
• c. Check charge using the electroscope.

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Charging by Contact
Touch sphere to white rod.
Remove white rod
Charge of sphere same as rod
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Electrical Units
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Coulombs Law
q
d
d
The force is positive if the charge on both
objects have the same sign and negative if the
sign of each charge is different.
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Coulombs Law
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Coulombs Law Restrictions

• 1. Objects need to be very far apart so that the
  charges are considered acting all from one point.

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Problems

• 1. Sample Problems p 588
• 1 2
• 2. Practice Problems p 589
• 1 2 3

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Gravitational Electrical Forces
Force
Attractive or repulsive
Attractive
Direction
Infinity
Range
Infinity
Relative Strength
1
1039
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Force of Electron on Proton in a Hydrogen Atom
Electrical
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Force of Electron on Proton in a Hydrogen Atom

• Gravitational

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Force of Electron on Proton in a Hydrogen Atom
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Problems

• 1. Sample Problems p 590
• 1 2
• 2. Practice Problems p 592
• 1 2 3
• 3. End of Chapter Problems 620
• 13 14 15 16 17 18 19

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Electric Fields ?
r
The direction of the Electric Field is in the
direction of the force on a positive test charge
due to charge Q that causes the electric field.
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Electric Fields ?

• Electric fields exert a force on an electrical
  charge that is in the field.

The direction of the electric field is in the
direction of the force on a positive test charge
q in electric field Q.
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Electric Field of Parallel Plates

• If the charges plates are close together
• 1. The intensity is zero in the region outside
  the parallel plates.
• 2. The intensity is constant everywhere in the
  space between the plates.
• 3. The magnitude of the intensity depends only on
  the magnitude of charge on each plate.
• 4. This is called a uniform electric field.

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Problems

• 1. Sample Problems p 596
• 1 2 3
• 2. Practice Problems p 597
• 1 2 3 4 5 6 7
• 3. End of Chapter Problems 621
• 20 21 22 23

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Electric Potential Energy Ee
Q
q
r
The electric potential energy is zero when the
two charged objects are an infinite distance
apart.
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Electric Potential Energy Ee
Q
q
q
r
8
If negative it means that the force between the
two object is attractive. Work is done and thus
energy is stored by moving them further apart.
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Electric Potential Energy Ee
Q
q
q
r
8
If positive it means that the force between the
two object is repulsive. Work is done and thus
energy is stored by moving them closer together.
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Electric Potential V
Q
8
r
Electric potential represents the amount of work
necessary to move a unit test charge from rest at
infinity to rest at any specific point in the
electric field of Q
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Potential Difference
Q
B
A
rB
rA
The potential decreases in the direction of the
electric field and increases in the opposite
direction.
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Parallel Plate Calculation
-
VAB
d

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Problems

• 1. Sample Problems p 602
• 1 2 3 4
• 2. Practice Problems p 603
• 1 2 3 4
• 3. End of Chapter Problems 622
• 24 25 26 27 28

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Electrical Formulae
Force
Field
Potential Energy
Potential
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Electric Field Inside a Sphere

• 1. Like charges dislike each other.
• 2. On a conducting surface the want to get as far
  away from each other.
• 3. Thus all charges end up on the outer surface.
• 4. Thus, the electric field inside the sphere is
  zero.

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Thats all folks!