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IrishJuniorCert
Static Electricity

Just a question regarding static electricity. When charging a metal conductor positively; it's relatively simple. A negative rod is put to the top of it, which causes the positive protons to move to the bottom and then a finger is used to earth the electrons at the top (while the rod prevents the protons from neutralizing it, allowing the electrons to leave). How do we negatively charge it though? Some marking schemes seem to say you do the exact same thing, but how can we earth protons? We learned in class that the protons will not be earthed; only electrons can be.


4 Comments
fogerred
fogerred
As far as I know, you would do the same procedure except hold up a positive rod. But it's a good point about protons not being able to be earthed
Somachi
Somachi
Basically: To charge a metal conductor positively you bring an already charged negative rod (or any object) towards the conductor. This induces a charge on the conductor (electrons are repelled from the rod and an area of positive and negative charge is created within the object). Then you earth the conductor (connect it to the ground) and the electrons will move into the ground. It's the same idea for charging a conductor negatively 1. Bring an already charged object of opposite charge towards it to induce charge (so bring a positive rode next to the object) 2. Then you connect it to the earth, in this case electrons move from the earth into the object giving the object a net negative charge. Why you bring a rod of opposite charge towards the conductors is because opposite charges attract. "Earth" is simply any larger body that can be used as a source of electrons or a way for the elctrons to escape.
RussianAndrey
protons dont move in this proccess or ever in static electrictiy or any other kinds of electricity
IrishJuniorCert
Somachi, that makes sense about the electrons moving from earth and getting a net negative charge. But you still will have a lot of positive protons there, you're not actually getting rid of them, right? So we're just increasing the number of negative charges, which kind of makes sense now.
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