If you’ve correctly chosen the direction of current, then their values will come out positive, like current should.

如果你正确地选择了电流的方向， 那么它们的值将是正的， 就像电流应该的那样。

But as the direction of current switches, the direction of both the electric and magnetic fields change.

但随着电流方向的改变，磁场和电场的方向也随之改变。

If you've correctly chosen the direction of current, then their values will come out positive, like current should.

如果你正确地选择了电流的方向，那么它们的值将会是正的，就像电流一样。