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Expert: Daniel Mazur - 3/2/2009


Question
Why did we chosen the direction of the current is in the direction of motion of the +ve charges although they are static  and not the direction of the electrons

Answer
Hello Mohamed,
this is because the choice (convention) was made before people knew about electrons in solids. In electrolytes current is carried by ions of both polarities, so there was 50-50 chance to pick the motion positive ones or negative ones as the conventional direction of the electrical current. Mind you, even the classification + and - of the ions is people's convention.
After electrons were found responsible for conduction in metals it was more convenient to stick to the old convention than having to translate all scientific articles before 1900 to a new convention.
Cheers,
Daniel

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Questions anyone (teenager, undergrad, graduate, professional) may ask on physics, mathematics or inorganic chemistry. Questions may concern subjects themselves or a possible future career in them, if you need advice on a school or hobby project, or you just came across a question that is beyond your current curriculum. I answer bare textbook problems sometimes, but I reserve the the right to redirect you to Physics-Physics section. The kind of questions I like to answer: I just started having science classes at school and they seem difficult, but I enjoy them. Where do I find more information on this, which is not in textbooks but still comprehensible to me? Just leaving high school, and I feel science is really the thing for me. Can you recommend a school and an undergrad program suitable to my inclinations? I am in my second undergraduate year in Physics. We learned the basics of universe expanding this year, the Hubble constant and all that, but invited speakers that gave talks on astrophysics in our department seemed not to agree with this model at all. Is it of any use at all? I am building a [materials research] experimental device for my masters/doctorate thesis and I have the following problem:... I have tried ..., but it still doesn't work. Where might the problem be?

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