Thursday, July 9, 2009

A +30 µC charge is placed 56 cm from an identical +30 µC charge. How much work would be required to move a....

A +30 µC charge is placed 56 cm from an identical +30 µC charge. How much work would be required to move a +0.50 µC test charge from a point midway between them to a point 14 cm closer to either of the charges?


__________ J

A +30 µC charge is placed 56 cm from an identical +30 µC charge. How much work would be required to move a....
The two source charges are Q=+30uC


The distance between them is r=.56m


The test charge is q=+.5uc





The potential at a point midway between the two source charges is defined as


V1=2KQ/(r/2) or v1=4kQ/r





and a potential at a point 14cm or .14m closer to either charge is


V2=kQ/(r/2)-.14 + kQ/(r/2)+.14





Work done by moving the test charge from V1 to V2 is





w=q(V2-V1)





=q(kQ/(r/2)-.14+kQ/(r/2)+.14-4kQ/r) pull out the k and Q


=kqQ(1/(r/2)-.14+1/(r/2)+.14-4/r





=(9e9)*(.5e-6)*(30e-6)*[1/(.56/2)-.14+...


=.321J


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