Electric Potential and Electric Potential Energy
Name___________________________________ Date_________ Hr. ___
To move charged particle in a uniform electric field requires ___________. In other words a force
must move over a distance. This will change the ______________ ____________ of the particle
in accordance with
Charge Q is moved from point A to
point B.
PEelectric =
If the charge is positive its potential
energy will decrease because its
ability to accelerate is reduced when it
is further away from the larger charged
particle .
+
Q
A
B
If the charge is negative its potential
energy will increase because its ability
to accelerate back towards the larger
charged particle increases when it is
further away.
Two charged particles positioned close together will also have potential energy as they attract or
repel each other. Similarly, without involving calculus we can write:
PEelectric =
It makes more sense to in fact talk about _____________ _______________rather than potential
energy. This is because we usually want to know what the effect will be on ________ charge
placed in an electric field.
This is defined as the amount of potential energy ______ ________ ____________ We can write:
V=
A potential difference can therefore be defined as:
V =
If the electric field is uniform:
V =
Unlike electric field strength, potential and potential energy are both __________ quantities. The
potential difference between two points does ______ depend on the ________ taken to move
between the two points.
Examples
1. A wire is connected to a 9V battery. How much potential energy does each coulomb of
charge have that is moving around the conductor?
2. A balloon rubbed on your head can be charged up to 5000V and hold a millionth of a
coulomb of charge. How much potential energy does this stored charge have?
3. A classroom Van de Graaff generator can easily be charged up to 50,000 V. Why is
touching the dome on the generator not dangerous to a human but sticking your finger in
a power outlet at 110 V is?
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4. The gap between electrodes in a spark plug is 0.060 cm. To produce an electric spark in
a gasoline-air mixture there must be an electric field of 3.0 x 106 V/m. What minimum
potential difference must be supplied by the ignition circuit to start a car?
5. In a thunderstorm, the air must be ionized by a high voltage before a conducting path for
a lightning bolt can be created. An electric field of about 1.0 x 10 6 V/m is required to
ionize dry air. What would the breakdown voltage in air be if a thundercloud were 1.60 km
above the ground? Assume that the electric field between the cloud and the ground is
uniform.