Consider Two metallic charged sphere whose radii are 20 cm and 10 cm respectively each having 150 microcoulomb positive charge. What is their common potential after they are connected by a conducting wire ?

Explanation

Shortcut method :
Note that the total on both the spheres is (150+150) =300 microcoulomb. When both the spheres will be joined by a wire they will have a common potential and the means `(q)/(4piepsilon_(e)R)` is same for both i.e larger sphere will have larger charger or you can say the total charge 300 microcoulomb will be divided into the radii ratio 1:2 . So the smailer sphere will have 100 `mu` C and the larger one will have 200 `mu` C

Now calculate the potential of any sphere say smaller one using equation `V=(q)/(4piepsilonR) = (100xx10^(-6)xx9xx10^(9))/(0.1) = 9xx10^(6)` volt and this will be common potential