What happens ac signal is earthed

 

Perhaps you would like to expand on your question?

 

I am going to make a wild guess that you are in India.

You should put your location in your profile. Click on "User CP", on the next page click "Edit Your Details", fill in the "Location" box with country and state or province, and click the "Save changes" button near the bottom of the page. This helps us to help you.

Here in the States, we have split phase power in homes. We get two "hot" lines and one "neutral" line coming into the dwelling. In Europe and many other countries, there is simply one "hot" line and one "neutral" line. The Neutral line is connected to earth ground at the electrical service panel/breaker box/fuse box, and that is the only place in the dwelling electrical system where neutral and earth ground are connected together.

Neutral should also be connected to ground by the power company. However, that ground may fail, so it is important that it be grounded at the dwelling.

If the ground connection fails, it is possible that the electrical system may "float" at thousands of volts, resulting in a very unsafe condition.

 

Personally, I would avoid referring to AC power as a "signal". I think that word is better used for something with an information or control content. Of course, usage in different countries (USA? India?) may be different.

That said, the question asked has so little information that it is hard to say what the OP wants.

What's going on here - do some Internet cafes charge by the keystroke?

 

We get many students from India on these "advanced" English-speaking forums.
I think they should chat with other students on "beginners" websites in India in their own language.

I helped a guy in The Philippines graduate from University and get a good job. We chatted on one of these forums about a project (his thesis) that didn't work at first, his English was pretty good and he had enough time on an internet cafe to fix it with me and demonstrate it.