1.3 Electric Force
Coulombs Law describes the electric force between charged objects.
Size:
Coulombs constant k = 9x109 Nm2/C2
Direction:
Opposite charges attract along line r.
Like charges repel along line r.
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Example:
Consider the ground state of a H-1
1
Motion of Charged Particles in E-Fields
A charged particle of mass m moving in a region of electric field experiences an
acceleration with a size of
If the electric field is uniform in this region then the acceleration is constant and
the equations of m
1.4 Electric Field
Symbol
E
mks units
[N/C]
A charged object with charge qo produces an electric field vector at every point in
space except at its position. This object exerts an electrical force on another
charged object with charge q. This force is giv
1.1: Review of Vectors
Review your vectors! You should know how to
convert from polar form to component form and vice versa
add and subtract vectors
multiply vectors by scalars
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Example:
Find the resultant vector R = r2 3r1 where r1 = 10 m, 45 and r2 = 2
Voltage (Potential)
Symbol
V
mks units
[Volts = V]
A charged object with charge qo produces a voltage at every point in space except
at its position. This object shares a potential energy with another charge q. This
energy is given by
where V is the volta
Continuous Charge Distributions
If point P is near a large charged object, then to find the electric field at P you chop
up the object into many point charges. You find the electric field due to each point
charge and sum up all these field vectors.
Exampl
1
Combinations of Resistors
Resistors in parallel share the same voltage difference.
The equivalent resistance of two resistors in parallel is
This equation can be solved for the equivalent resistance to give
-Resistors in series have the same current flo
Symbol
I, i
mks units
[Amperes = Amps = A = C/s]
The current is the rate that charge flows from one point to another.
By convention, current flows in the direction that positive charge would travel in a
circuit. (In practice, it is the flow of electrons i
A capacitor is a device that can store opposite charge (+Q and Q) on two different
surfaces when a voltage difference (V) is applied between the surfaces. The
capacitance (C) of the capacitor determines how much charge can be stored for a
given voltage di
Positive charges speed up when going from high to low voltage. They slow down
when going from low to high voltage.
Negative charges speed up when going from low to high voltage. They slow down
when going from high to low voltage.
Using the previous equati