Electric fields are responsible for another type of potential energy. Charges can move
“uphill” or “downhill” in the field.
Energy is stored in the arrangement of charges. Capacitors can store a lot of energy
that can be quickly discharged.
Muscle and nerve cells have large electric fields. Depolarization of nerve and muscle
cells produces externally measurable fields.
Pushing a Stone Uphill
Suppose you need to roll a stone to the top of a hill.
What factors determine how much force you need to apply?
What factors determine how much work you need to do?
Height of hill
Electric Forces and Electric Potential Energy
A +1.0 nC charge sits at a certain point in the earth’s field, which is 100 N/C, directed
What is the direction of the force on the charge?
If the charge is moved upward, the electric potential energy will be increased (moving
Potential Energy and Potential
Potential difference: how high is the hill?
The potential is the potential energy “per charge”
V = q
The change in potential energy when a charge goes through a potential difference ΔV
ΔU elec qΔV Units: J/C, or volts (V)
We generally look at differences in potential; a difference in potential ΔV is called a
Connecting Field and Potential
In a uniform field, moving a distance Δd produces a chan