All conductors (with rare  exceptions) have some resistance to the flow of electric current, and that creates heat which will  eventually damage the conductors and insulation if it builds up.

所有导体（除了极少数例外）对电流的流动都有一定的阻力，这会产生热量， 如果热量积聚， 最终会损坏导体和绝缘层。