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

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

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

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

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

Potential is Scalar

Electric Field and Potential §19.4

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

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

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