1. The problem statement, all variables and given/known data a positivly spheric charged ball is placed on an isolating tripod. its going to be used to measure the voltage between 2 paralell metaldiscs. trough a tiny hole in the lower metaldisc the ball reaches in to 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. 2. Relevant equations E(N/C)=F/Q E=(k*Q)/r^2 E=F/Q 3. 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 wich 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!