Download Key Points on “electric potential”

Key Points on
“electric potential”
Electric Potential …
• “electric potential” is used to refer to the
voltage present on a point due to near by
charges. They may ask for the “potential
difference” as well.
V=kq/d OR V=Ed OR V= E/q
V is voltage
K is constant
E is electric field
q is charge
d straight line distance to test charge
• Electric Potential and Potential Difference
are most easily identified in a battery OR a
circuit tied to a battery.
The battery supplies the circuit with the
same “potential” as listed. For example, a
9V battery has chemical potential to move
charges (q) from the negative terminal to
the positive terminal and out to the circuit.
• Multiple charges in an area have the
potential to influence a nearby charge.
For example: What is the electric potential
in volts at point If each of the
represent a 3.5nC charge and are located
at the corners of a 4cm by 4cm
square?
• Two disks, each with a radius if 1.5cm, are
charged to ±0.885nC. What is the electric
field strength of the capacitor? (this is a
concept from chapter 26) What is the
potential difference across the capacitor if
the spacing between the disks is 2.5mm?
• An electron with an initial speed of
800,000m/s is brought to rest by an
electric field. What is the potential
difference that stopped this electron?
Key Points of
“Electric Potential Energy”
• Remember that potential energy is the
result of the situation that is at hand. For
example, a book on top of the side cabinet
has higher potential energy than a book
laying on the ground due to the “situation
or position” it is in.
• Charges can create “electric potential
energy” because of the situation or
arrangement they are in.
If a charge is in a “voltage” situation….U=qV
U is potential energy in Joules
q is charge
V is voltage
• If there is not a “test charge” present, an area can still
have electric potential energy due to the interactions of 2
or more charges.
If these two + 2.6nCcharges are placed 5.5cm apart, their
potential energy is based on charge value and distance
of separation through the formula:
U= kq1q2 /d
• If there are more than 2 charges in an
area, you must account for all charges and
their influence on each other. If
represents +3.0nC charge and
represents a -1.5nC charge calculate the
net potential energy in the following figure.
Each leg of the triangle is 4.5cm
• Watch for verbiage!!!
Potential energy = Joules = U
Electric potential = potential difference=
voltage = V