Transcript electric potential

Name two ways that the electromagnetic force and
gravitational force are different.
Notes on Electric Potential
Electric Field
notes
Imagine we have the Earth and a
large asteroid as shown below.
What will happen to the asteroid? Why?
Notes on Electric Potential
Electric Field
notes
Imagine we have the Earth and a
large asteroid as shown below.
What will happen to the asteroid? Why?
It will be drawn toward
the Earth and impact it
from Earth’s
gravitational field.
Notes on Electric Potential
Electric Field
Now imagine we have the charges shown
below.
1C
-1,000 C
What will happen to the + charge? Why?
Notes on Electric Potential
Electric Field
Now imagine we have the charges shown
below.
1C
-1,000 C
What will happen to the + charge? Why?
It will get pulled to the
negative charge
because of their
electric field.
Notes on Electric Potential
Field Lines
So how do we draw this? The type of
charge matters, so we need some way of
showing direction and strength. We do
this with field lines.
Notes on Electric Potential
Field Lines
So how do we draw this? The type of
charge matters, so we need some way of
showing direction and strength. We do
this with field lines.
Scientists decided a long time ago that
lines should go out from positive and in to
negative.
The vectors always point in the direction
of the force that would act on a small
positive test charge placed in the field
Notes on Electric Potential
Field Lines
There are 3 things we need to know
about field lines:
1) + charges move in the direction of the
arrow, - charges move backwards.
2) The more closely packed the arrows
are, the stronger the electric field is.
3) Unlike gravity, electric field lines can
be blocked.
Notes on Electric Potential
Electric
Shielding
Metal and conductors shield or change
our field lines. This is because electrons in
metal can move very easily. Since they
can move very easily, they try to spread
out into the best configuration possible.
Notes on Electric Potential
Electric
Shielding
Metal and conductors shield or change
our field lines. This is because electrons in
metal can move very easily. Since they
can move very easily, they try to spread
out into the best configuration possible.
Example: a charged, hollow sphere
–
–
–
–
–
–
–
– –
–
+
–
–
–
–
–
–
– – –
The charge spreads evenly, no matter
where we place the charge inside!
Notes on Electric Potential
Electric
Shielding
Example: a charged, hollow cube
––
–
–
–
–
–
–
+
–
–
––
– ––
–
–
–
–
–
–
The charge spreads out to get close to the
positive, bu away from other negatives.
This causes more to cluster on corners.
Notes on Electric Potential
Electric
Shielding
Example: a charged, hollow cube
––
–
–
–
–
–
–
+
–
–
––
– ––
–
–
–
–
–
–
The charge spreads out to get close to the
positive, bu away from other negatives.
This causes more to cluster on corners.
Faraday Cage
If we put charges inside a box like this, we
can tell how intense the charge is, but not
where it's located since it evens out. Places
like the FBI make use of this a lot.
Notes on Electric Potential
Electric
Potential
Just like how we have gravitational
potential energy, we can have electric
potential energy.
Think of it like gravity.
Positive charge wants to flow “downhill”.
Negative charge wants to flow “uphill”.
Notes on Electric Potential
Electric
Potential
Assuming same charges, the farther we
get from a charge, the less potential we
have. We can draw lines of equipotential
around charges. These are like elevation
on a map. Charges can move on an
equipotential line without using energy!
e-field lines
High potential
equipotential
Low potential
circles
Notes on Electric Potential
Electric
Potential
move charges around
Electric
Potential
formula
Notes on Electric Potential
Electric
Potential
move charges around
Electric
Potential
formula
Equations
Change in
=
voltage
work done
___________
charge
Work (J)
Charge (C)
Voltage (V)
equations
Equations
Electric Field
Strength
V
or m
vocab
Vocabulary
Electric Field
The field created by charges that affects all
other charges nearby.
Field Lines
A way of showing what the electric field looks like
around a charge.
Conductor
An object that has free-flowing electrons. These
can also shield electrical fields.
Equipotential
Places or curves in an electric field that have the
same electric potential energy.
Electric
Potential
The energy a charge can gain or lose by flowing
“uphill” or “downhill” along field lines.
Volt
How much energy can be loaded on each Coulomb
of charge.
Exit Question #6
Which way do electric field lines and potential lines run?
a)
b)
c)
d)
e)
f)
Both go from + to Both go around a charge
Potential goes from + to -, field lines go around a charge
Potential goes from - to +, field lines go around a charge
Field lines go from + to -, potential go around a charge
Field lines go from - to +, potential go around a charge