# quiz3 - e q i q j/r ij ⇒ W = k e Q 2/a x-1 1-2 √ 2-2-1...

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Name: ________________________________ ID#: __________________________________ Physics 7D Disc. TA: ____ __________ ________________ Quiz Ch.25 Version B Date: _______________ Hour:_____________ Four charges with magnitude Q are positioned at the corners of a square with side length a, as shown below. a) What is the work done by an external force in assembling the charges, assuming that they start very far from each other (at infinity)? Work done is ½ times the sum of k
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Unformatted text preview: e q i q j /r ij . ⇒ W = k e Q 2 /a x { (-1+1-2/ √ 2) + (-2-1/ √ 2 +1) + (2-2/ √ 2-2) + (-1-1/ √ 2 +2) }/2 = - k e Q 2 /a {3/ √ 2} b) What is the electric potential at the center of the square? The electric potential is k e times the charge divided by the distance to the point at which the potential is evaluated, summed over all charges. In this case it is given by: k e Q √ 2/a (1-1-1+2) = √ 2 k e Q/a a a a a +Q +2Q -Q-Q...
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