why negative and positive terminal is used
Please find the link below for solution to the similar query
https://www.meritnation.com/ask-answer/question/electrons-are-negatively-charged-ions-how-they-are-able-to/academics/1030962
Regards
https://www.meritnation.com/ask-answer/question/electrons-are-negatively-charged-ions-how-they-are-able-to/academics/1030962
Regards