Electrostatics and Electromagnetism Flashcards Preview

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Flashcards in Electrostatics and Electromagnetism Deck (25):
1

Charge, conductors, charge conservation

Charges are either positive or negative. Zero charge is neutral.
Like charges repel, unlike charges attract.

Charge is quantized, and the unit of charge is the Coulomb.

Conductors are materials in which charges can move freely. Metals are good conductors.

Charge is always conserved. You can't create or destroy charge, you can only transfer charge from one source to another.

2

Insulators


Insulators are materials in which charges can not move freely. Nonmetals are good insulators.
 

3

Coulomb's law

4

Electric Field Lines


Lines that are closer together denote stronger fields than lines that are farther apart.
 

5

Electric Field Due to Charge Distribution: Dipoles

6

Electric Field Due to Charge Distributions: Same Charges

7

Electric Field of a Capacitor

8

Electric Field for positive Wire

9

Electrostatic Potential for a positive charge

10

Electrostatic Potential for a negative charge

11

Absolute potential (V)

Absolute potential (V) is the amount of energy per charge that something possesses.


V = U/q0 = kq/r
 

12

Potential difference (ΔV)

Potential difference (ΔV) is the difference between two potentials.


ΔV = VB - VA
 

13

Equipotential lines


Equipotential lines are places where the potential is the same. 

Equipotential lines are always perpendicular to electric field lines.
 

14

Electric Dipole


dipole = a positive charge and a negative charge separated by some distance.
 

15

Behavior of an electric dipole in an electric field


A dipole in an electric field will want to align itself with the electric field, such that the positive end of the dipole is in the direction of the electric field.
 

16

Potential due to Dipole

To calculate the exact potential at a given point, just calculate the individual potential due to the positive charge and the negative charge, then add them together.

17

Electrostatic Induction

18

Gauss' Law


  • ΦE = EA cosθ

    • ΦE is electric flux.

      E is electric field, A is area that the field goes through, and θ is the angle between the field and the normal of the area.
       
  • ΦE = q/ε0

    • For an enclosed surface, the electric flux is equal to q, the charge inside the enclosure, over the permitivity of free space. 




    • The net electric flux through any enclosed surface is totally dependent on the charge inside. If there's no charge inside, then the net electric flux through the enclosure is zero.
       

       

19

Faraday Cage

Basically, the electric field inside a closed conducting cage is zero. This is because the charges on the conducting cage will rearrange to cancel out any external field.

20

Definition of the magnetic field B


Magnetic field B exists in a region of space if a moving charge experiences a force due to its motion in that region. 




The unit for magnetic field is the Tesla (T) or N·s/m·C
 

21

Existence and direction of force on charge moving in magnetic field

 

22

Charge moving in a circle


F = qvB = mv2/r 




You are setting the electromagnetic force equal to the centripetal force, which maintains the orbit. Using this equation, you can solve for whatever the question asks you.
 

23

Current carrying wires


F = qvB sinθ = (it)vB sinθ = (it)(L/t)B sinθ = iLB sinθ
 

24

Right Hand Rule

 

 



Using your right-hand: 
point your index finger in the direction of the charge's velocity, v, (recall conventional current). 

Point your middle finger in the direction of the magnetic field, B.

Your thumb now points in the direction of the magnetic force, Fmagnetic.

 

 

25

Properties of electromagnetic radiation 

  • radiation velocity equals constant c, in vacuum
    • Electromagnetic radiation travels fastest in a vacuum, at a velocity equals c, or 3x108m/s
       
    • Light slows down when it travels in a medium other than in vacum. n = c/v, where n is the index of refraction for the medium, and v is the speed of light travelling in that medium.
       
  • radiation consists of oscillating electric and magnetic fields that are mutually perpendicular to each other and to the propagation direction

A image thumb