If you do an influence test with an electroscope when you approach a negative rod, the electrons will move away when this electroscope is grounded due to the repulsion that prevails. If you do an influence test with an electroscope when you approach a negative rod , when this electroscope is grounded, the electrons leave due to the repulsion that prevails. So I was wondering if there wasn’t that repulsion, or if there was attraction, then the electrons don’t move away when grounded.
Answer
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The electrons that flow to earth with a negative rod in the vicinity of the electroscope do so because for them the neutral earth is more positive than the negative proximity of the rod. As a result, the electrons in the electroscope are thus attracted to the earth and repelled from the rod. The electrons want to get as far away from that negative rod as possible. (They “want” nothing, of course, but the resultant force has that effect.)
If that rod is not there and there is no other charge in the vicinity, then no electrons transfer from the earth to the electroscope or vice versa, because the electrons on the electroscope and on the earth feel the same electrically neutral field at the electroscope as on the earth . There is no resultant force pushing the electrons one way or another.
If you approach the electroscope with a positive rod, for example, you have the opposite effect. I am attaching a figure for clarity. Electrostatic induction or influencing then attracts electrons from the (neutral) earth to the electroscope, which is in a positive field. The electroscope therefore becomes negative as a result, but you only see this when you remove your finger from the electroscope, because the charges then redistribute over the whole.
Answered by
ir Ineke De Coninck
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