Phys: Chapter 20: Electric Forces And Fields

Front 1

Charge model

Back 1

1. Frictional forces like rubbing add or remove charge. More rigorous rubbing produces a larger quantity of charge
2. There are two kinds of charge, positive and negative
3. Like charges repulse each other. Opposite charges retract each other.
4. the force between two charges is long ranged. The magnitude of the force increase as the quantity of charge increases and decrease as the distance between the charges increases.
5. Neutral objects have an equal mixture of positive and negative charge. The rubbing process somehow manages to separate the two

Front 2

Charge is conserved

Back 2

Charge can neither be created nor destroyed

Front 3

conductors

Back 3

materials through or along which charge easily moves

Front 4

Insulators

Back 4

materials on or in which charge remain immobile

Front 5

Note

Back 5

Both insulators and conductors can be charged. They differ in the mobility of the charge

Front 6

Electrostatic Equilibrium

Back 6

Charges are at rest and there is no net force on any charge. Isolated conductors reach static equilibrium

Front 7

Charge polarization

Back 7

Bringing a charge near a neutral material cause the like charge in the material to run away and the opposite charges to run towards the charge. So even though the neutral material remains neutral, charges separate, or polarize to opposite ends of the material. These effect is more profound with conductors, but it also applies to insulators.

Front 8

Charge model

Back 8

1. Frictional forces like rubbing add or remove charge. More rigorous rubbing produces a larger quantity of charge
2. There are two kinds of charge, positive and negative
3. Like charges repulse each other. Opposite charges retract each other.
4. the force between two charges is long ranged. The magnitude of the force increase as the quantity of charge increases and decrease as the distance between the charges increases.
5. Neutral objects have an equal mixture of positive and negative charge. The rubbing process somehow manages to separate the two

Front 9

Charge is conserved

Back 9

Charge can neither be created nor destroyed

Front 10

conductors

Back 10

materials through or along which charge easily moves

Front 11

Insulators

Back 11

materials on or in which charge remain immobile

Front 12

Note

Back 12

Both insulators and conductors can be charged. They differ in the mobility of the charge

Front 13

How would you explain how charged things exert on attractive force on neural objects

Back 13

The attractive force that accounts for this is the polarization force, which arrises from the polarization of the charges within the neutral object. As some charge approaches, charges within the object separates, or polarizes.

Front 14

Ionization

Back 14

The process of removing an electron from an electron cloud

Front 15

e (Fundamental charge)

Back 15

- The same in magnitude for protons and electrons, but opposite in charge
e= 1.6 * 10^-19 C

Front 16

Current

Back 16

motion of a charge through space

Front 17

charge carrier

Back 17

The charges that physically move

Front 18

(Induced) electric dipole

Back 18

charge polarization on the atomic scale. When an external charge induced polarization within the atom. The "orbits" of the atom know oblong, and the electrons now hang out closer or further from the external charge, depending on whether the external charge is positive or negative

Front 19

Coulomb's Law

Back 19

F= K|q1||q2|/r^2
Where the force is an action/reaction pair. That is, force of 1 on 2 is equal to the force of 2 on 1.
Magnitude of the charges only,
The force is repulsive for like charges and attractive for opposite charges.
K (the electrostatic constant) is 9.0 * 10^9 Nm^2/C^2

Front 20

Coulomb's Law and point charges

Back 20

point charge have a mass and a charge, but they do not have have a volume. Two charges can model a point charge if their size is much smaller then the distance between them.

Front 21

Coulomb's law and force

Back 21

gives only the magnitude of the force. The direction depends on whether the charge are alike of opposite

Front 22

Electric forces

Back 22

Are vectors. Which means you can treat them as vectors, add them vectorally... If multiple charges are present, the net electrical force is the sum of the forces produced by each individual charge.

Front 23

Field

Back 23

The general term for the warping of space around a charge, if its an electric field, a magnet, if its a magnetic filed, and a mass, if its a gravitational field. The field itself is the agent that exerts a force on something else. If a force is a push or a pull, then the electric field is the thing that does the "pushing"

Front 24

Field Model

Back 24

1. Some charges, which we will call source charges, alter the space around them by creating electric fields, E (vector arrow).
2. A separate charge in the electric field then experiences a force F(vector arrow) exerted by the field.

Front 25

Electric Filed (the algebraic definition for)

Back 25

Electric field varies with each coordinate point in three-dimensional space. Electric field for a charge q who experiences a Force F (on q):

E at (x, y, z) = (F (on q) at (x, y, z)) /q

Front 26

Electric filed units

Back 26

we are describing F/charge so the SI units:

N/C

Front 27

Electric field strength

Back 27

The magnitude of the magnetic field

Front 28

Electric field

Back 28

there is an electric field vector at every point

Front 29

Electric field

Back 29

does not depend on the charge size (or the charge magnitude) It only depends on indentity of the source charge

Front 30

Electric Field Lines (RULES)

Back 30

1. Filed line can never intersect
2. The spacing of the field lines is proportional to the strength of the field at that point.
3. Line are always begin at a positive charge and end at a negative charge
4. The number of lines connected to a charge is proportional to the magnitude of the charge
5. The test charge is a positive charge
6. The lines represent force vectors, not the path a particle will take.
7. The vector (of one point) is the vector sum of all the charges in the field on our test positive charge

Front 31

Electric Field and the relationship between the sign of F and the sign of E

Back 31

E = F/q
The electric field vector has the same direction as the force vector on a positive charge and the opposite direction to that of the force vector on a negative charge.