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Zamze
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Homework Statement
a positivly spheric charged ball is placed on an isolating tripod. its going to be used to measure the voltage between 2 parallel metaldiscs. trough a tiny hole in the lower metaldisc the ball reaches into the homogen field. the ball and the isolated tripod are on top of a scale. the values on the scale are registered. after that the charge on the metal discs are turned off and the scale numbers are read again.
calculate the voltage between the 2 metaldiscs if the balls charge is 12nC (12*10^-9) and the difference in the scale measurements are 0.25g. the distance between the discs are 5cm.
Homework Equations
E(N/C)=F/Q
E=(k*Q)/r^2
E=F/Q
The Attempt at a Solution
i found out that E=(mg)/Q but this still didnt help me. (E here is for electric field strenghts)
so i tried k which is 8.99*10^9.
(k*Q)/r^2 and got 43142 N/C for E.
then my E*d = 2157 volt,
so then i involved E=(mg)/Q
(E*Q)/9.82 and got m = 5.25*10^-5.
and since delta m is 0.25g i did my m + delta m and got 3.027*10^-4.
this i then used as U/d=F/Q with my new m value.
so (mg)/Q = 247709
this i multibplied with d, 0.05 and got 12385. so the closest thing i can come up to, to reach the answer 10kV is 12385-2157. but i wouldent exactly understand why :/.
thanks in advance!
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