Soln4 - Electric Potential - 8B Worksheet Answers 4....

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8B Worksheet Answers 4. Electric Potential 1. a) 1.44 × 10 4 Coulombs, or about 9 × 10 22 electrons. b) The larger D-cell contains more total chemical energy than the smaller AA-cell, and thus will move more charge over its lifetime. If we want to push through the same current, this means the D-cell will last longer. 2. a) The electric potential energy can be defined to be anything when the charge is released, since we haven’t specified a ‘reference point’ for potential. (It would be like asking how high something is without saying weather you want the height relative to the ground, sea level, your roof, etc.) Only changes in potential matter! If we choose a convention such that the V = 0 line is where we set the zero of potential energy, then the particle has a potential energy of qV = 24 Joules. b) Object will move in the direction that lowers their potential energy. c) Electric potential energy is Δ U = q Δ V . q is positive and we want Δ U to be negative, so that means Δ V must be negative - the positive charge wants to move towards lower electric potential. In the case shown, the charge will move to the left . d) v = 2 q ( V i " V f ) m = 8 m/s e) The electric field always points towards lower potentials (it points in the direction of the force that a positive test particle would feel), so the field points towards the left. f) Parts (b), (d) and (e) remain the same. For part (a), if we again chose the zero of potential energy to be the zero of electric potential, then the potential energy will be qV = -24 Joules. For part (c), since q is negative, we want Δ V to be positive
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This note was uploaded on 10/16/2010 for the course PHYS 8B taught by Professor Catherinebordel during the Spring '10 term at University of California, Berkeley.

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Soln4 - Electric Potential - 8B Worksheet Answers 4....

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