June 9, 2022

Tech Secrets: Nobody Knows Which Way Current Flows

Understanding electric current has led to an incredible lift in the average person’s quality of life. From cooking and lighting to ensuring sewage systems are working properly, there are no limits to the benefits that understanding and utilizing electricity have had. However, if you take a survey of electronic engineers and scientists and ask them which way current flows, you’ll find some say from the positive to negative and some say from the negative to positive.

What Gives?

This is a strange phenomenon involving something very important – the core of every electronic device is controlling the flow of electronic current to ensure some useful outcome. The current is the middleman between the input request and the output. It made sense to scientists that current could be produced and flow from the positive to the negative, something that was known as conventional current flow.

That sounds reasonable, but an aspect of current that is under no debate is what current actually is – it is moving electrons. What are electrons? They are little subatomic particles with a negative charge. It is basic physics that negatively charged ions are attracted to positive charge, so later on, in the mid-1900s, electronic technicians during World War II decided that it made more sense that the electrons are attracted to positive charge, so current must flow positive to negative. This informed all US engineer training materials, so after the war, the belief that the electron flow dictated the current flow became widespread.

Why Is This Important?

It doesn’t matter so much which current direction an electronic engineer uses, as circuit analysis works for both assumptions. It certainly doesn’t matter with AC components. However, DC, which comes with monodirectional flows, can affect the theory behind components. For example, TRIACs (both for DC and AC), which conduct current in both directions, rely on applying positive or negative bias current to the gate, so for the scientists who truly want to understand the electronic components they work with, the directional flow of electric current is an important theoretical issue.

The Flow of Current

If the current was universally dictated by electrons, the issue might be more straightforward, but what throws a spanner in the works is the involvement of other particles. When a battery is connected to a copper wire, the positive terminal of the battery pulls the electrons off the top atomic layer of the copper atoms. The copper atoms become positively charged, pulling more electrons towards it and instigating flow. However, there are exceptions to electron movement. Sometimes whole ions contribute to the current, like in some semiconductors and even in batteries. In these instances, the flow is not dictated by the electron movement but actually by the lack of an electron (and therefore a positive charge). That means the flow of the current goes from negative to positive. Materials with these properties are called P-type materials, referring to their positive charge.

The fact that P-type materials are named P-type implies that the majority of electrical current flows from positive to negative, and this is difficult to deny. Something propagating the debate is the exceptions to the rule, as well as the fact that conventional current flow is still taught in many engineering schools.

About the author 

Elle Gellrich

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