What colour wire is used for earthing or grounding?

State one main difference between $AC$ and $DC$. Why is $AC$ preferred over $DC$ for long-range transmission of electric power? Name one source each of $DC$ and $AC$.

How many times does an $AC$ electric current with the frequency $50\, Hz$ change its direction in one second?

Name two safety measures commonly used in electric circuits and appliances. What precautions should be taken to avoid the overloading of domestic electric circuits?

Mention the voltage and frequency of the electric current that we receive in our houses.

Differentiate between overloading and short-circuiting.