1. SCI 340 L41 Potential potential energy per charge
Electric Potential
potential energy per charge
§19.1–19.2

2. Electric Potential Field:force as potential:potential energy
Field is force per charge
Potential is potential energy per charge
Unit = J/C = volt = V

3. Electric Potential
What is the work required to move a charged object through a field?
higher e
lower e Dx
Work = qE·Dx = D(PE) = qDV
V = electric potential = PE/unit charge

4. The electron volt (eV) Work done on 1 C by 1 V = 1 J
Work done on e by 1 V = 1 eV
e = 1.60210−19 C, so 1 eV = 1.60210−19 J

5. Potential Near a Point Charge
Define r = ∞ as potential of 0
Work needed to bring a test charge qT (1C) in from infinite separation to a distance r from charge q is:
W = r
kqqT
therefore
V = W/qT = r kq

6. Potential is Scalar

7. Electric Field and Potential
§19.4

8. Potential and Field
Equipotential surfaces are always perpendicular to electric field lines/vectors. Why?
Potential changes rapidly where field is strong. Why?
It makes sense from the relationships between
Electric field and electric force
Electric potential and electric potential energy
Work and potential energy
Force and work

9. Voltage We seldom care about potential energy itself
The important quantity is energy difference
Voltage is electric potential difference between two points
A voltmeter measures voltage

10. Potential vs Voltage Potential is at one point
relative to some reference
reference is usually infinite separation
Voltage is between two points
Or across the path between them