Electronics/Conventional Current

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Electronics | Foreword | Basic Electronics | Complex Electronics | Electricity | Machines | History of Electronics | Appendix | edit

An electronic circuit is a system in which electrons flow from a negative terminal of a source, through a load, to the positive terminal. Unfortunately for electronics students, pioneers in the fields of electricity and magnetism believed that positive charge flowed, so many of the conventions in physics and electronics assume that current flows from positive to negative, even though the particles that are moving are actually negatively charged electrons moving from negative to positive. (conventional current is covered in the voltage and current section. should we take it out of here and just leave it there?)

Talking about conventional current here sounds like a good idea. The discussion should include a blurb on the relationship between conventional current and voltage.

If you are having trouble imagining this, consider what happens if you pass helium filled balloons to another person while you both are standing on scales. If the balloons are very large, then the person receiving the balloon actually loses weight and you who gave the balloon gain weight -- as measured by the scales. (This is because the balloons are pulling up on you.) In other words, the person who gives the balloon seems to have received weight and the person who receives the balloon seems to have lost weight. In the same way, when something gives electrons it seems to have received positive charge.

If this all seems confusing, rest assured that you will find a way to think about it that works for you. Many people just ignore the electrons altogether and think of positive charge flowing around. Except in rare cases this is completely fine.

So, different types of negative particles drift from negative to positive, and positive particles drift in the opposite direction, at different speeds in different materials. How to make sense of this? Conventional current. We define current as flowing from positive to negative, and ignore the particles that make it up (for most purposes), paying attention only to the amount of charge flow per unit time, and the speed of the electromagnetic waves. We will sometimes still talk about electrons flowing, since they are the predominant charge carriers in metal, and many circuit components. Just keep these principles in mind.

Current i / I is represented in Amperes / Amps / A and equals x number of y