# What is opposite of electric field?

A negatively charged molecule will generate a field, an electric field, and it will repel all negative ions.

So what does positively charged molecule generates that causes other positive molecules to be repelled?

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Yes, you can think of it that way. But more generally, it is called simply "the electric field" and its sign, magnitude, and relation to position all depend on the source charges and where the charges are. For more details, look at hyperphysics.phy-astr.gsu.edu/hbase/electric/elefie.html. The sign of $Q_source$ is what changes the sign of the electric field. –  mcFreid Dec 30 '13 at 1:09