Download Electric Potential and Electric Potential Energy

a) proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. Which
feels the larger electric force?
b) electron
c) both feel the same force
d) neither – there is no force
e) they feel the same magnitude
force but opposite direction
Electron
electronProton
+

E
proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. Which
feels the larger electric force?
a) proton
b) electron
c) both feel the same force
d) neither – there is no force
e) they feel the same magnitude
force but opposite direction
Since F = qE and the proton and electron
have the same charge in magnitude, they
both experience the same force. However,
the forces point in opposite directions
because the proton and electron are
oppositely charged.
Electron
electronProton
+

E
proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. Which
has the larger acceleration?
a) proton
b) electron
c) both feel the same acceleration
d) neither – there is no acceleration
e) they feel the same magnitude
acceleration but opposite
direction
Electron
electronProton
+

E
proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. Which
has the larger acceleration?
a) proton
b) electron
c) both feel the same acceleration
d) neither – there is no acceleration
e) they feel the same magnitude
acceleration but opposite
direction
Since F = ma and the electron is much less
massive than the proton, the electron
experiences the larger acceleration.
Electron
electronProton
+

E
proton
a) proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. When it
strikes the opposite plate, which
one has more KE?
b) electron
c) both acquire the same KE
d) neither – there is no change of
KE
e) they both acquire the same KE
but with opposite signs
Electron
electron
-
Proton
+

E
proton
A proton and an electron are in
a constant electric field created
by oppositely charged plates.
You release the proton from the
positive side and the electron
from the negative side. When it
strikes the opposite plate, which
one has more KE?
a) proton
b) electron
c) both acquire the same KE
d) neither – there is no change of
KE
e) they both acquire the same KE
but with opposite signs
Since PE = qV and the proton and electron
both have the same electric potential energy
Electron
electron-
initially. Because energy is conserved, they
Proton
have the same charge in magnitude, they
both must have the same kinetic energy after
they reach the opposite plate.
+

E
proton
• Small group whiteboard task:
• On 1 half of the whiteboard:
• Draw a diagram of a spherical mass and its gravitational field lines
• Write the equations for gravitational field strength, gravitational
potential energy, and gravitational potential
• Discuss the definitions of each of these concepts
• On the other half of the whiteboard:
• Draw a diagram of a positive point charge and its electric field lines
• Write the equation for electric field strength
• Predict the equations for electric potential energy and electric
potential
• Determine a definition for electric potential energy and for electric
potential
• The energy stored in an electric field in the space
between two charged objects.
𝑘𝑞𝑄
𝑈=
𝑟
• Units: Joules / J
• The work done, per unit positive charge, to move a positive test
charge, q, from infinity to some position, P, away from an object
with charge Q.
∆𝑉
• Also related to electric field strength: 𝐸 = −
∆𝑥
• And: 𝑉 =
𝑘𝑞
𝑟
• Which also means that: ∆𝑉 =
• Units = Volts / V
∆𝐸𝑝
𝑞
• If a positive test charge is used as the reference charge, where
would it have the highest potential?
• Near a positive charge
or
• Near a negative charge
• Why?