Which way ARE we going?
The Direction of current flow.
There are events in technology and science that are confusing more confusing than they ought to be. Once we realise that such confusions are not made to confuse us and we find out how they occurred in the first place, we will be able to deal with them with better understanding and less frustration.
In electricity, for many people there is a confusion about the direction of the current flow. Is it going from positive to negative or from negative to positive, and, what do we mean by 'conventional current'? Can the electric current go both ways? Is there a simplified explanation that makes sense so we can remember it? Let us find out.
The early pioneers invented the first electric battery. They concluded that the copper element (carbon rods later) in batteries must be 'rich in electrons' and the zinc 'poor'. So copper became the positive terminal and for many years it was assumed that the current went from positive to negative.
In 1904 British electrical engineer J.A. Fleming noticed that an Edison electric light bulb, (which, as you know, has a hot filament) when fitted with an additional cold element inside the bulb, allowed the current to flow in only one direction. It became a rectifier. Also he found that the current moved the opposite way from what was accepted formally. Electrons move from the heated cathode (see Fig. 1) to the cold anode. By now it was too late to rename all the thousands of batteries and appliances that had been built and so we are stuck with the fact that the current in reality always flows from minus (negative) of the power source to plus (positive).
FIG. 1
I know there are different interpretations of electron flow. Some teachers and text books talk about 'conventional' and 'real' current flow directions. In fact, even semi-conductors seem to point in the direction from plus to minus as indicated by the diode in Fig. 2.
FIG. 2
I suggest to simplify the issue and make it possible for us to analyse diagrams and understand how components react - without confusion - let us remember that
THE CURRENT ALWAYS MOVES
FROM NEGATIVE
TO POSITIVE.
A 'conventional current flow' does not exist. It is like saying steam is going into the boiling water in the kettle and becomes water. It simply is not so.
Please remember, I am always keen to hear your ideas, questions and feedback. You are most welcome to contact me, Peter on my mail address.
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Copyright © 1997-2010 Peter Schmedding, Child Development Projects, Canberra, Australia.