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What are the two types of electric charges?
How do the charges interact with each other?
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Define Nucleus and Electron Cloud
The atom is held together by the attractive _______ force between the positive ______ and negative ______
- Nucleus: The very small and dense core of an atom, containing positively charged protons and neutral particles called neutrons
- Electron Cloud: surrounding the nucleus, formed by less-massive negatively charged electrons
- electric force
- positive nucleus
- negative electrons
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Electrons and protons have charges of opposite sign but exactly equal ________. An object is charged if it has a(n) _______ number of electrons and protons. Protons are extremely ______ bound within the nucleus. They cannot be ______ to or ______ from atoms. Electrons are bound much more _______ than protons and can be removed with _____ effort
- magnitude
- an unequal
- tightly
- added to or removed from atoms
- loosely
- little effort
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The SI unit of charge is the _______ (__).
♦ e is the _______ unit of charge, called the _______ charge (except for _____)
♦ e = _________
♦ So 1C needs _______ electrons or protons
- coulomb (C)
- smallest
- elementary charge
- quarks
- e = 1.6*10-19C
- 6.24*1018
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The charge on an object can only be a whole number of ±e's; that is, charge is ________. For any object, its charge is always equal to ______, where n is a ______ number. Electric charge is usually denoted by the letter q (or Q):
q = ______, where n = ___, ___, ___,...
- quantized
- n(±e)
- whole number
- q = n(±e), where n = 0,1,2,...
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Define:
Ionization
Cation
Anion
The net charge in an isolated system is always ________. For example, charge is NOT _______ in the process of rubbing two objects together. What causes the electrification?
- Ionization: the process of removing an electron from the electron cloud of an atom
- Cation: positive ion, an atom that is missing electrons
- Anion: negative ion, an atom the has extra electrons
- conserved
- NOT created
- The electrification is due to a transfer of electron
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- q = nmol(±e)
- q = n(+e)
- q = (6.022*1023)(+6 protons)(1.6*10-19) = 3.613*1024(e)
- q = n(-e)
- q = (6.022*1023)(-6 electrons)(1.6*10-19) = -3.613*1024(e)
Total charge: (3.613*10 24e) + (-3.613*10 24e) = 0
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Define Electrical conductor
Free ______ are not bound to the atoms. These ______ can move relatively freely through the material. Examples of good conductors include ______, ______ and ______. What happens to the charge when a good conductor is charged in a small region?
- Electrical conductors: materials in which some of the electrons move relatively freely.
- electrons
- electrons
- Copper, Aluminum and Silver
- The charge readily distributes itself over the entire surface of the material
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Define Electrical insulators (or _______)
Examples of good insulators include _______, ______ and _____.
What happens to charge when a good insulator is charged in a small region?
- Electrical insulators (or dielectric): materials in which electric charges are tightly bound to the positive nuclei and not free to move around
- Glass, Rubber and Wood
- The charge is unable to move to other regions of the material
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Visualizing Charge
1. The rod and wool are initially _______ (explain)
3. Now we rub the plastic and wool together. As we do so, negative charge moves from the _____ to the ______
4. This leaves the rod with extra ______ charge. The wool is left with more ______ charge than ______
5. In a charge diagram, we draw only the _______ charge. This shows how the rod and wool acquire their charge.
- neutral
- Neutral actually means that they each have equal amounts of positive and negative charge.
- wool to the rod
- negative charge
- positive change than negative
- excess charge
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Charges on an ______ do not move. Charges on a _______ adjust until there is no net force of any charge. We call this ________ _______
- insulator
- conductor
- electrostatic equillibrium
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1. The 1st metal sphere ________ charge.
2. In the 2nd set, the metal sphere to the left is ______. While the metal sphere to the right is _______
What can be said of these spheres?
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The electrical properties of ___________ are somewhere between those of insulators and conductors.
semiconductors
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Examples of semiconductor materials include _______ and ________. The electrical properties of semiconductors can be changed over many orders of magnitude by adding controlled amounts of ______ _____ to the materials
- Germanium and Silicon
- foreign atoms
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Forces from the external charge cause the atom's negative charge and the positive charge to be slightly ______.
Define Electric Dipole
An external charge will cause polarization of an atom to become an ______ ______ ______.
Some molecules have an asymmetry in their charge distribution that makes them _______ _______ _______. Eg. _____ molecule
- slightly offset
- Electric Dipole: Two equal but opposite charges with a separation between them
- induced electric dipole
- permanent electric dipoles (eg. Water molecule)
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In water, the electrons spend more time with ______ than ______, so the oxygen end is slightly ______. The hydrogen end is slightly _______. The slightly negative oxygen is attracted to the slightly _______ hydrogen of a neighbor. This allows for ______ bonds with neighboring water molecules
- oxygen
- hydrogen
- negative
- positive
- positive
- hydrogen bonds
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When a glass rod is rubbed with silk, electrons are transferred from the ______ to the _____. Each electron adds a negative charge to the _____. An equal positive charge is left on the _____. This is because of _______ _____ ______
- glass
- silk
- silk
- rod
- conservation of charge
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Neutral metal rod acquires a charge when placed in contact with a ______ ______ object, this is called ______ ______
- charged metal object
- electrical conduction
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When a conductor is connected to Earth by means of a conducting wire or pipe, it is said to be _______. We can charge a conductor by a process known as charging by _________. Charging an object by induction requires _____ ______ with the object inducing the charge
- grounded
- induction
- requires no contact
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Inducing a Charge on an Object Connected to Ground
(a) The neutral metal rod is still neutral, not charged.
(b) The charged rod only separates the charge in the ______ ______ ______. However, it is ______ ______
Electrons flow from ______ to the _______ if the charged object is positive, and from the ______ to the _______ if the charged object is negative. If the neutral metal rod is connected to the ground, the charged rod will induce ______ charge in the grounded rod
- neutral metal rod
- still neutral
- ground to conductor
- conductor to ground
- opposite charge
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A process similar to induction can take place in ________. The process is called ______ _______(define). The charges within the molecules of the material are _________.
- insulators
- charge polarization: A slight separation of the positive and negative charge in a neutral object when a charged object is brought near
- rearranged
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Why does the charged rod attract paper?
We can say the polarization force between a charged object and a neutral one is _______ _______
- The paper is attracted to the rod because a charge separation is induced in the molecules of the paper
- always attractive
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Label the diagram
How is each electroscope charged
A _______ ______ ________ can be used to determine the sign of a charged object
A previously charged electroscope can be used
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A. The neutral metal sphere will be attractive because its a metal, the charge can rearrange allowing for the attraction
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- Positive: B
- Negative: A
- Neutral: C & D
*check notes for illustration
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- -e = -1.6*10-19C and you've gained 5*1010 of them, charge on hand will be:
- q = (5*1010)(-e) = (5*1010)(-1.6*10-19) = -8*10-19C
- Since the cat has lost 5*1010 electrons, the charge on the cat will be:
- q = (5*1010)(+e) = (5*1010)(+1.6*10-19) = 8*10-19C
**Note that the net charge before and after petting the cat was zero; all you've done is transferred charge
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The force between two charged objects is a ______ _____ force. The electrical force between two stationary charged particles is given by ________ ______. The force is ________ ________ to the square of the separation r between the particles and directed along the line joining them. The force is ________ ________ to the product of the charges, q1 and q2, on the two particles.
Electrostatic equilibrium refers to the condition that the charges in an _______ ________ are at rest
- long-range force
- Coulomb's Law
- inversely proportional
- directly proportional
- isolated conductor
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State 3 formulas for Magnitude of Force in Coulomb's law
What is the meaning/value of:
ke (2)
ε0 (1)
Direction: The forces are directed along the line _______ the two particles. Either repulsion or attraction depends on the _____ of the two charges
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- joining
- sign
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In vector form,
_____ is a unit vector directed from q 1 to q 2.
The two like charges produce ______ forces between them
The two opposite charges produce ______ forces between them
Depict the 3 possible scenarios
- repulsive forces
- attractive forces
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Coulomb's law applies only to _____ _____. Electric forces, like other forces, can be superimposed. The resultant force on any one particle equals the ______ _____ of the individual forces due to all the other ________ particles.
**Remember to add the forces as vectors
The resultant force on q 1 is the ______ _____ of all the forces exerted on it by other charges:
- point charges
- vector sum
- individual
- vector sum
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State the strategy for solving problems with Coulomb's Law (8-story)
Prepare (4)
Solve (3)
Assess (1)
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- a) q/r2
- b) 2q/(2r)2
- c) 2q/r2
- d) q/(2r)2
- C is the largest
- D is the smallest
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- The closer charge will be longer so
- A) The minus charge radiates inwardly, pulling the small charge toward the left (↞) at a higher magnitude because it it closer. The plus charge radiates outward pushing the small charge toward right (→) at a lower magnitude because its farther away. Hence, the resultant force will be toward the left
- B) The negative charge will radiate inwardly, pulling the small charge toward the left (←) and is farther away so has a weaker magnitude. The positive charge radiates outwardly pushing the small charge toward the right (↠). The resultant force will be toward the right
- C) The near plus charge radiates outwardly, pushing the small charge to the left (↞). The plus charge further away does the same but with a weaker magnitude (←). The resultant force will be to the left
- D) ↞ ↠, both radiate inward with the same magnitude and equal proximity from the position of the small charge. Neither wins so its neutral or zero. Points directly between like charges have neutral or practically zero force acting on them
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