 As you lift an object off the ground, you are increasing its potential energy  Same is for electric potential ◦ Electric potential ( Δ V)  Work done moving a test charge in an electric field by dividing the magnitude of the test charge  Δ V = W / q (Work is the Potential energy need to remove the charge over some distance = joules) ◦ Measured in joules /coulomb (J/C = Volt (V))

 Work is required to push a charged particle against the electric field of a charged body.  EPE is the energy a charge particle possesses because of its location in an electric field.  If the particle is released it will accelerate away turning the EPE into kinetic energy.

 If you apply 150 J of work to move a positive charge of 3.5 x C from a negative plate, what is the electric potential difference?  Known ◦ Work on q = 150 J ◦ q=3.5 x C  Unkown ◦ΔV◦ΔV ◦ Δ V = W / q = 150 J / 3.5 x C ◦=◦=

 Electric Potential ◦ Smaller when two unlike charges are closer together ◦ Larger when two like charges are

 Uniform electric force and field made by placing 2 large conducting plates parallel to each other ◦ Direction is from + plate to –plate  Potential difference, Δ V, between 2 points a distance (d) apart, in a uniform field (E)  Δ V = Ed

 2 Parallel plates are given opposite charges. A voltmeter measures the EPD to be 60.0 V. The plates are 3.0 cm apart. What is the magnitude of the electric field between them?  Known ◦ Δ V = 60.0 V ◦ D = m  Unkown ◦ E = ???

 E = V / d  = 60.0 V / m  = 2.0 x 10 3 N/C

 Storing energy in an electric field ◦ Leyden Jar ◦ Developed by Dutch physicist Pieter Van Musschenbroek  Used by Ben Franklin to store charges from lightning  Version is still used today: Capacitor

 Ratio of charge stored to electric potential difference: called Capacitance, (C)  Capacitor designed to store electric charges and energy ◦ Made of two conductors separated by an insulator ◦ Capacitance = charge / electric potential difference ◦ C = q / Δ V ◦ Measured in Coulomb per volt (C/V) or 1 Farad (F)

 A sphere has an eletric potential difference between it and Earth of 60.0 V when it has been charged to 3.0 x C. What is the capacitance?  Known ◦ V = 60.0 V ◦ q = 3.0 x  Unknown ◦ C = ???

 C = q / Δ V  = 3.0 x / 60.0 V  = F  = 0.05 µF

 Examples: crank/shake flashlight, computer keyboards, flashes in cameras, electronics.