Which Way is the Field?

When a battery is connected to a wire there will be a non-zero field inside the wire and charges will flow.

For the charge carriers in a metal, the applied field superimposes a net drift velocity vd onto the random motion already there.

If the colored balls represent conduction electrons in a metal, in which direction is the applied field when the field is turned on?

  1. to the left
  2. to the right














If you turn on the field and watch the purple ball (which represents a typical electron) for a while, you should notice a net drift to the right. The field must therefore point to the left, because that would generate a force to the right on negative charges.