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Building circuits.  Circuits seem like such a magical thing.  And they really are.  But for the sake of learning, it’s useful to stop believing that they are magic, as it gets in the way of learning that they are actually easily understood if we go through the explanations step-by-step.  Of course, some of the real low level questions won’t be answered; you’ll just have to take that for granted.  If you continue to follow questions backwards and ask ‘why’ about everything, eventually you’ll reach a point where humans do not yet have the answer.  An example:  why do atoms even have electrons?  Why are positive and negative charges attracted to each other?  How could there be nothing before the big bang?  Isn’t nothing still something? I won’t be answering these questions.  They aren’t really relevant most of the time in engineering either, so don’t let the little things ruin you.  At a certain point you just need to accept the facts, gather yourself, and move on with your life.  Remember, engineering is applied science, so we focus on applying the principles but let the scientists in lab coats figure out the nitty gritty details.

Circuits.  You wire together several different components in a seemingly nonsensical way, wires looping every which way, a transistor or several hundred, give it a power source, and watch it do your bidding.  A simple circuit might light up a small LED light.  A more complicated circuit lets you send an email from your phone.  But behind both, many of the same principles are at play, just on a different scale and with a variety of different components used.  The different components are really there to each do a job, and we will find out what each one does individually, and how they all come together to function and work together.  Most textbooks or articles online will start by talking about voltage, current, resistance, and ohm’s law.  That is a good place to start.  But it is not the very start, so let’s go back a bit further.  Understanding the building blocks a little better means that the rest of the concepts will have a better foundation.  Then these concepts can get a firm grasp in your memory, and you won’t just be able to just recite these ideas on demand under duress such as in job interviews, but rather truly understand it.  And that is the goal; memorization is mostly useless in the context of learning (and this is why the majority of tests and exams should be open book).

At the most basic level, electricity is a type of energy.  Energy is familiar; all living organisms need a source of energy to live and operate, to do work.    We need energy to move around everyday, to go to the gym, to sit and watch television.  We don’t run off electricity, but we could if we were designed differently – robots certainly use electricity, usually from batteries, to move around and perform tasks.

Also remember that energy can be converted from one form to another – we can exert energy on something such as a hand-crank radio and convert the motion of our hand and arm (kinetic energy) into electricity.  Calories as the input from the food we eat, light as the output from the flashlight.  Or we can put a solar array on the flashlight, capture the energy from the sun, and convert that to electricity to power the flashlight. Sunshine as the input, light as the output.  So electricity isn’t as scary as it first seems.  It is not a difficult concept, just one that seems improbable at first.  Who would have thought that the flow of electric charge commands such an incredible power.

So what is this electric charge then?  What is electricity?  Read on!

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