Electric potential energy please help?

2016-09-10 8:28 am

The electric potential energy of a neurtral object is zero. The electric potential energy of two unlike charges placed nearby is negative. Rubbing a plastic rule with a cloth will make them carry unlike charges. Can we conclude that charging an object by friction will cause a loss in electric potential energy of the system? If not, how do you account for the apparent loss in energy?

回答 (1)

天同

2016-09-11 6:10 am

✔ 最佳答案

You need to be aware that -ve energy is only a relative concept. It helps to distinguish between attractive force field and repulsive force field. Objects possess -ve energy do not mean they have no energy. In the example of two unlike charges quoted by you. If the two charges are connected by a conducting wire, current will flow and energy is released.

In that example, when the two unlike charges are brought together forming a system, -ve work needs to be done by an external agent (external force). In other words, energy is absorbed by that external agent. This situation is different from the example of charging an object by friction. Surely, charging by friction needs the work done by an external agent, and heat is usually produced during the charging process as well.

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