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Unformatted text preview: Physics 21 Spring, 2011 Solution to HW5 242 The electric potential difference between the ground and a cloud in a particular thunderstorm is 1 . 7 × 10 9 V. What is the magnitude of the change in the electric potential en ergy (in eV) of an electron that moves between the ground and the cloud? Electric potential energy difference for a particle can be cal culated using the following relation: Δ U = q Δ V where q is the charge of the particle and Δ V is the elec tric potential difference. Note the difference between elec tric potential , and electric potential energy . Briefly, electric potential is unit energy per unit charge, so it can be defined for any point in an electric field independent of any actual charges. For an electron, q = e , so: Δ U = q Δ V = 1 . 7 × 10 9 eV 244 Two large, parallel, conducting plates are 13 cm apart and have charges of equal magnitude and opposite sign on their facing surfaces. An electrostatic force of 3 . 2 × 10 − 15 N acts on an electron placed anywhere between the two plates. (Ne glect fringing.) (a) Find the electric field (in N C ) at the posi tion of the electron. (b) What is the potential difference in volts between the plates? Equation 221 tells us that the electric field due to some electrostatic force is E = F q so plugging in (a) E = F e = 3 . 2 × 10 − 15 N 1 . 602 x 10 − 19 C = 2 . 00 × 10 4 N C Equation 2418 tells us that the potential difference between two points is found with the equation Δ V = integraltext E · d s since the electric field is constant between the plates, we can write Δ V = E Δ s or the potential difference equals the electric field times the seperation between the plates. Plugging in gives us (b) Δ V = parenleftbigg 2 . 00 × 10 4 N C parenrightbigg * . 13 m = 2600 V 249 An infinite, nonconducting sheet has a surface charge...
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This note was uploaded on 02/07/2011 for the course PHY 21 taught by Professor Hickman during the Spring '08 term at Lehigh University .
 Spring '08
 Hickman
 Electric Potential, Energy, Potential Energy

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