Physics 2 Ch 21 Electric Potential
the mass of a proton is
1.67x10^-27kg
Kf+qVf = Ki+qVi
1/2mvf^2 + qVf = 1/2mvi^2 + q Vi
The unit of electric potential is the joule per coulomb, called the volt V
1volt = 1V= 1J/C
conservation of energy for a charged particle moving in an electrical potential V
Kf+qVf = Ki+qVi or Kf + (Uelec)f = ki (Uelec)i i and f = intial and final
Ex. 21.3
P= change in E/ change in t
Capacitance of the capacitor
The constant of proportionality C between Q and delta Vc
Relationship between electric potential and electric potential energy
Uelec= V/q
Change in Us = W
Us = elastic potential energy
charge q's electric potential energy remains unchanged as it is moved from A to B, so (Uelec)B=(Uelec)A(Uelec). Then, because Uelec=qV, it must be the case that
VB=VA. We say that the potential difference ΔV=VB−VA is zero.
change Ug = W
W = work Ug= gravitational potential
The entire conductor is at the same potential, and thus the surface is
an equipotential surface.
any two points inside a conductor in electrostatic equilibrium are
at the same potential.
Thermal energy (Eth)
change Eth = -q change V
Kf-Ki = -q(Vf-Vi) rewritten
change K = -q change V
electric potential energy (Uelec) is represented as
change Uelec = W
When we say "A capacitor has charge Q," we mean that one electrode has
charge +Q and the other charge −Q.
Microvolts (μV)(μV), millivolts (mV)(mV), and kilovolts (kV)(kV) are
commonly used units.
The electric field points in the direction of
decreasing potential.
a system's energy can be changed by
doing work on it
The plates of a parallel-plate capacitor are connected to a battery. if the distance between the plates is halved, the energy of the capacitor
doubles
the only way that no work can be done is if the
electric field is perpendicular to the equipotential.
the energy is stored in the capacitor's
electric field.
The voltage of a battery is the difference in
electric potential between its two terminals.
A charged capacitor stores energy as
electric potential energy.
the two conductors that make up a capacitor are its
electrodes, or plates
The movement of the charge stops when change in Vc is
equal to the battery voltage. The capacitor is then fully charged
The electric field at a point is perpendicular to the
equipotential surface at that point.
A negative charge speeds up if it moves into a region of
higher potential
a positive charge speeds up as it moves from
higher to lower potential
if q<0 requires k to
increase as V increases
As the particles move away from each other, the potential energy
increases, so the kinetic energy decreases
when a particle with positive charge q moves from a region of high electric potential to a region of low electric potential, its electric potential energy decreases and its kinetic energy
increases.
The dipole moment points in the direction of
increasing potential
The electric field
inside is zero.
The electrical potential is created by the source charge. The electric potential is present whether or not a charged particle
is there to experience it. Measursed in J/C or V
A positive charge slows down (K<0) as it moves from lower to higher potential (V>0). kinetic energy
is transformed into electric potential energy
Removing an electron from a spherical atom
means separating a small negative charge from a sphere that has a positive charge
the force on q'q′ is quite large when it gets near q, so the work required to move it through the same small displacement is
much greater than before.
A capacitor with a large capacitance holds more charge for a given potential difference than
one with a small capacitance.
The electric potential energy is the interaction energy of a charged
particle with the source charges. Measured in J
The exterior electric field is
perpendicular to the surface.
A potential difference is created by separating
positive charge from negative charge.
A positive charge speeds up (K>0) as it moves from higher to lower
potential (V<0). Electric potential energy is transformed into kinetic energy
A double headed green arrow is used to represent a
potential difference
the charge of a capacitor is directly proportional to the
potential difference between its electrodes
The potential difference between the electrodes is called the
potential difference of the capacitor.
a charged particle's potential energy is
proportional to its charge.
the potential difference between the electrodes is directly
proportional to their charge.
Because it moves along an equipotential, its potential and hence its potential energy are the
same at the beginning and end of its displacement. (No work is done moving the charge)
The field strength is largest at
sharp corners.
E represents
the constant electric field (V/m)
d represents
the distance between plates
x represents
the distance of the point from the negative plate
The field strength is inversely proportional to the spacing d between
the equipotential surfaces
The SI unit of capacitance is
the farad
the potential of an electric dipole is the sum of the potentials of
the positive and negative charges
delta V
the potential difference between the plates
Any excess charge is on
the surface.
a capacitor can be used
to store charge
capacitor
two conductors with equal but opposite charge
The capacitors energy is stored in the electric field in
volume Ad between the plates
change Uelec = W
we can determine the electric potential energy of a charge when it's at a particular position by computing how much work it took to move the charge to that position.
a charged capacitor holds energy until
we discharge it.
