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Gravitational Electric EElectric vs. Gravitational g Potential Potential Energy Energy Increases Increases - + • Work is needed to • Work is needed to push an object push a charge against against gravity and a field and give it give it Potential Electric Potential Energy Energy
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Potential DifferencePotential Energy & Potential Difference Voltage (scalar or vector) Divide both sides by qo What does voltage and you get another actually measure? physical quantity: – Measures how much Electric Potential! energy a charge will Otherwise known as gain/lose voltage! – Measures how much work that can be done by a charge If the Electric Field is constant, it comes out of the integral and you get V = Ed
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Allesandro VoltaUniform Electric Fields (Italian: 1745 – 1827) Parallel Plates Point charge Note the field lines Uniform electric field
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Battery gives the electron 12 J of Potential energy e “loses” energy as it travels through the circuit.Analogy 12 V 0V Battery “gives” energy back to electron to repeat cycle
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• Sample ProblemPotential Energy & Potential Difference A 9 V battery is connected to two parallel plates that are separated by a distance of 0.30 cm. a. What is the electric field? b. How much energy would an electron have when placed next to the positive plate? + + + D = 0.04m – – p+ – a) V = E d b) Ue = q ∆V 9 = (E)(0.003m) = (9 V)(1.6 x 10-19C) Ue = 1.44 x 10-18 J E = 3000 V/m
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