MadSci Network: Physics

Re: What direction does the current flow in a DC circuit?

Date: Mon Feb 7 13:26:10 2000
Posted By: Frank Berauer, Technology Transfer Engineer Microelectronics
Area of science: Physics
ID: 949866131.Ph

Dear Alan,

You are right, there is some confusion about the direction an
electric current is flowing.
When electricity was discovered, nobody knew how it works and
electrons were unknown. So the scientists just defined one of
the poles as "positive" and said that the current is flowing
from positive to negative. That still is the definition of an
electrical current's flow direction.
However, later scientists discovered that in most (but not all)
materials current is carried by negatively charged electrons,
which travel from negative to positive. The electron flow is
thus opposite to the current flow.
In some materials (e.g. electrolytic solutions) the current is
carried by positive ions, which travel in the current's direc-
tion. And in semiconductors there can be currents of negative
or positive carriers, depending on the doping.

Greetings from Singapore,
        Frank Berauer

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