1. The problem statement, all variables and given/known data I never quite understood the principles of earthing, but I think that the general idea is that if you have an object with excess charge (whether positive or negative), then connecting it to the earth with a conductor will mean that either the excess electrons flow to the earth (if object is negatively charged) or electrons flow from the earth to the object (if the earth is positively charged) and that this happens until both the earth and object have the same charge density, but because the earth is so large this means that all of the electrons from the object end up flowing to the charge, or as many electrons as are needed to make the positive object neutral flow to it. I have two questions about this: 1. Is the effect of earthing difference if your object is an insulator with charge gathered on it, or is it is a charged conductor? 2. In my text book, it says that 'an earthed conductor will become charged is a charged object is placed near it'. Should it not be that the charge then flows to the earth so neither the object, nor the conductor next to which the object is placed, end up with a charge? 2. Relevant equations n/a 3. The attempt at a solution My guess for the first question is that for an insulator it depends on whether the insulator is earthed at the point on its surface where charge is stored, because here the excess electrons may be able to just move enough to get to the earthing lead, but it depends on how good an insulator it is. But I'm not sure... For the second question, I have no idea :( Thank you in advance!