Question

what is electrification and how is repulsion a sure test of it...???

Answer 1

Electrification is the process of powering by electricity and is usually associated with changing over from another power source. The broad meaning of the term, such as in the history of technology and economic history, usually applies to a region or national economy. Broadly speaking, electrification was the build out of the electrical generating and distribution systems which occurred in the United States, Britain and other countries from the mid-1880s until around 1940 and is in progress in rural areas in some developing countries. This included the change over from line shaft and belt drive using steam engines and water power to electric motors.
The electrification of particular sectors of the economy is called by terms such as factory electrification, household electrification, rural electrification or railway electrification. It may also apply to changing industrial processes such as smelting, melting, separating or refining from coal or coke heating or chemical processes to some type of electric process such as electric arc furnace, electric induction or resistance heating or electrolysis or electrolytic separating.
Electrification was called "the greatest engineering achievement of the 20th Century" by the National Academy of Engineering.

Answer 2

2 opposite charges always repel........bt attraction may also take place due to induction.......e.g when comb over dry hair attracts hair.............none is charged bt comb still attracts hair........due to the induce positive charge in hair and negative in comb.....

another example is
plastic rod over silk