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Electric Energy and Current Chapter 17

Electric Energy and Current Chapter 17. Electrical Potential Energy- the potential energy between charges at a distance, or between a charge and an electric field. ∆PE = -qEd As a charge moves, it gains KE, and loses PE. Potential Difference- the work that must be done to move a charge.

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Electric Energy and Current Chapter 17

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  1. Electric Energy and Current Chapter 17 Electrical Potential Energy- the potential energy between charges at a distance, or between a charge and an electric field. ∆PE = -qEd As a charge moves, it gains KE, and loses PE.

  2. Potential Difference- the work that must be done to move a charge. • Many different names- Potential, Potential Difference, Voltage, Emf. Symbol is V, units are V = J/C. DV = DPE/q DV = -Ed V = kq/r In order to have energy stored, you must keep the terminals of the battery at different potential (ie different levels of charge)

  3. The gap between electrodes in a spark plug is .060 cm. Producing an electric spark in a gasoline-air engine requires an electric field of 3x106V/m. What minimum potential difference must be supplied?

  4. Capacitance- the abilityof a conductor to store energy in the form of electrically separated charges. • Symbol is C, unit is the Farad, F. • C = Q/V 1 Farad = 1 Coulomb/Volt • Parallel plate Capacitor (most common) C = e0A/d A=area, d= distance between plates e0= 8.85 E-12

  5. A capacitor connected to a 12V battery source hold 36μC of charge on each plate. What is the capacitance?

  6. Capacitance can be changed by putting something between the plates of a capacitor. We call this a dielectric. • A dielectric is an insulating material- examples are glass, rubber, wood, waxed paper, etc. Molecules in dielectric become polarized, line up with electric field. This allows for a weaker electric field between the plates, so the plates can store more charge. • Capacitance increases with a dielectric.

  7. An example of a capacitor is the flash in a camera. • Energy stored in a charged capacitor • PE = ½ QV • Since Q = CV, PE = ½ CV2 • Usually capacitance and charge are small units • pF = 10-12 F • nC = 10-9 C • mC = 10-6 C

  8. Find the electrical potential energy stored in the capacitor in the previous problem

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