Electric Potential Energy PE q E d PEelectric

Electric Potential Energy • PE= -q. E d • PEelectric= -q. Ed charge electric field strength displacement from a reference point in the direction of the field • Only for a uniform field • Another type of Mechanical Energy

Positive charge moves d through a uniform field E + + d Figure 18 -2 from p 667

Potential Energy: Electric vs Gravity PEelectric = -q. E d PEgravity = mg h m h d earth

Unit analysis PE= -q. Ed • joules = coulombs newtons/coulomb meters so • E is sometimes in so and

Potential Difference • Potential difference is the change in electric potential measured in volts • V = Units: volts=J/C • V=-E d Units: volts= *m

Potential Difference in Charges and Fields sim -4. 4 V 2. 2 V/m

Capacitors • Device that stores charge • Capacitance is a measure of the ability to store energy in the form of separated charges

Capacitance Equations Q = total charge Units: farads = C/V 0 = permittivity constant (C 2/Nm 2) A = area of plate d = Distance between plates

Energy and Capacitors Equations