Chapter 19 Flashcards Preview

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Flashcards in Chapter 19 Deck (26):
1

Polarization

Atoms rotate in response to an external charge. This is how a charged object can attract a neutral one.

2

Insulators

Charges cannot move, will usually be evenly spread throughout object

3

Conductors

Charges free to move, on isolated conductors all charges move to the surface

4

Charge if by conduction

A charged object is placed in contact with another object. Some electrons move from one to the other, leaving the both objects with the same type of charge.

5

Charging by induction

Requires no contact with the object inducing the charge, a grounded conducting wire is connected to allow electrons to move from the sphere to the ground and when the wire is removed the charge object is left with a sign opposite that of the charging object

6

Grounded

An object connected to a conducting wire or pipe to the ground, allows movement of electrons

7

The electric force between two charged particles:

-is inversely proportional to the square of the distance between particles
-increases if the magnitude of charges increases
-is attractive if the charges are of opposite sign and repulsive of the charges have the same sign

8

Coulomb’s Law

The strength of the force between two objects is determined by the charge of the two objects

9

Law of Superposition

The total force on the object is just the vector sum of the individual forces

10

A vector field...

...gives magnitude and direction

11

Electric fields

-the force, F, on any charge q0 due to some collection of charges is always proportional to q0

12

Electric field

A quantity, which is independent of that charge q0, and depends only upon its position relative to the collection of charges

13

A field...

...is something that can be defined anywhere in space. It can be a scalar or vector field

14

I’m electric field maps and lines...

-lines leave + charges and return to - charges
-the test charge is positive
-number of lines in map = amount of charge
-tangent of line = direction of E
-density of lines = magnitude of E

15

The field is only zero on an electric field lines map when

Between two charges of the same type

16

Excess charges in conductors:

-free to move
-repel each other
-end up on the surface

17

Conductors at equilibrium

-no moving charges
-E=0 inside
-electric field perpendicular to the surface

18

Conductors and shape

-more charges at sharper curves
-E is larger there
-easier to accumulate charge in pointy objects

19

Electric flux

Measures E perpendicular to the surface, units N•m^2/C

20

Flux of a point charge +q

-E=kq/r^2 radially outward
-choosing a sphere centered on q
-E is perpendicular to the surface, A

21

Gauss’s Law

-defining permittivity of free space
-electric flux through a closed system is proportional to the charge enclosed by the surface
-flux=4(pi)kq=q/€0

22

Charged plate

-symmetry: E is perpendicular to the plate
-uniformly charged
-so E has a constant magnitude

23

Electric field distributions

Dipole: ~1/R^3
Point charge: ~1/R^2
Infinite line of charge: ~1/R

24

Infinite line of charge

-symmetry: Ex=0
-sum over all elements
-electric field produced is everywhere perpendicular to the line, proportional to the charge density, decreases as 1/R

25

Infinite plane

-symmetry: Ex=Ey=0
-sum over all elements
-the electric field produced is everywhere perpendicular to the plane, proportional to the charge density, and constant in space

26

Two infinite planes

-same charge but opposite
-fields of both planes cancel out outside
-the add up inside
-perfect to store energy