How to change polarity of current?

Answer 1

You might be asking the wrong question. In North America, utilities deliver 120 volts AC at 60 hertz. This means the voltage at your electrical outlet rises to positive 60 volts and then goes to negative 60 volts. The 60 hertz means this happens 60 times a second.

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If you mean you have an outlet with hot and ground or hot and neutral reversed, you should call an electrician. You can buy a cheap tester that will plug in to show you if you have a receptacle mis-wired this way. If the receptacle has a black and white wire connected, and the black wire is not the "hot" wire, it can be tricky to trace down the problem.

Answer 2

To change the polarity of current, simply reverse its direction, positive for negative and negative for positive.

Of course, if you have any direction sensitive components, such as diodes, in the circuit, this will not work.