What is the potential difference between two concentric charged spheres?

AI Thread Summary
The discussion revolves around calculating the potential difference between two concentric charged spheres. The user correctly identifies the formula for potential difference as ΔV=k*(Q/R - q/r) but is confused about the resulting value. Clarification is sought on the calculation of potential difference, emphasizing that it represents the work needed to move a unit charge between the two spheres. The user has successfully determined the charges on both spheres after connecting them with a wire but struggles with the potential difference calculation. Understanding the work involved in moving a charge is essential for resolving the confusion.
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Homework Statement


In the figure, a metal sphere with charge q=https://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2561214entrance1_N10031.mml?size=14&ver=1471825532267&algorithm=1&rnd=1471825539091 μC and radius r=https://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2561214entrance1_N1003F.mml?size=14&ver=1471825532267&algorithm=1&rnd=1471825539091 cm is concentric with a larger metal sphere with charge Q=https://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2561214entrance1_N1004D.mml?size=14&ver=1471825532267&algorithm=1&rnd=1471825539091 μC and radius R=https://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2561214entrance1_N1005B.mml?size=14&ver=1471825532267&algorithm=1&rnd=1471825539091 cm. (a) What is the magnitude of the potential difference between the spheres? If we connect the spheres with a wire, what then is the charge on (b) the smaller sphere and (c) the larger sphere?

Homework Equations


V=k*(q/r)

The Attempt at a Solution


I got b and c correct, it is just part a that I am confused. The question ask for the potential difference between the two sphere, so i simply took the difference. ΔV=k*(Q/R - q/r)=7.8E5, please help me understand why this is not the correct answer. Thanks
 

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The potential change (difference) is the work it takes to move a unit of charge from one point to another. How would you calculate that work?
 
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