Electronic Components Part 3: R

V = IR

Welcome to the third part. This will cover resistance. For us armature electronic engineers the component that we will use the most are resistors. Every circuit uses resistors. Actually, every circuit uses capacitors too, but not as frequently as resistors.

Resistors, as the name implies, cause resistance in the circuit. Using our hydraulic analogy, think of a resistor as a crimp in the pipe that restricts the flow of water. This is measured in ohms.

So V is the pressure, I is the rate of flow, and R is the resistance of the flow.

Let's set up a simple circuit consisting of a power source (V) and one resistor, and an ammeter.

Lets say we are using a 10 volt battery and we have a 100 ohm resistor.

Using simple algebra we can rearrange V=IR to solve for I. I=V/R.

I = 10/100

I = 0.1 amperes (amps), or 100 mA. This is the reading we would see on the ammeter.

If we increase the resistance and keep V the same, the current will decrease. If we decrease the resistance, the current will increase.

It is actually much harder to under stand the "why" than it is to do the math with this equation.

The next installment will be an introduction to the various electronic components that you will frequently see in a circuit.

Electronic Components Part 2: I

Time for part 2 of this thing: Current. I is the second term in V=IR (obviously). It is also the one thing about electricity that scares the crap out of me. When it comes to electrical shocks, the current is what makes them deadly.

Current describes the rate of flow on the electrical charge. It is the change in coulombs (electrical charge)/change in time. Going back the the hydraulic analogy, current is the flow rate of the water. Current is measured in amperes (A).

This is a quick post. Next week will be R (resistance), and I will also bring everything together for an explanation of Ohms Law.

Electronic Components Part 1: V

One of the most basic (an most useful) equations in the worlds of electronics is V=IR, known as Ohm's Law. The first three posts will be about the three components of this equation. I will try my hardest to explain everything as simpily as I can. I want this to serve as a solid foundation to build upon in order to cover more complex topics. I want to adress the "why" for these topics too, not just show you equations and how to use them.

The first component of V=IR is V. This is the voltage. It is sometimes represented by an E, short for electromotive force, but that is not quite relevant yet. Just call it voltage for now. A voltage is the electrical potential difference between two points. Now, what does that mean?

Lets say you have closed "circuit" of pipes and the whole thign is full of water. you are able too measure the pressure at two points in this circuit, point A and point B. With the water not moving in the pipes, the two pressures will measure the same. Now, lets add a pump between points A and B. When you turn the pump on the water will start to flow. The pump creates a high pressure area and a low pressure area. Now measure the pressure at points A and B and you will find a pressure difference. If the pipes were actually copper wire and the water electrons, the difference in pressure would be the voltage. This is part of the hydraulic analogy of eletrical circuits. For some reason I was not taught this, but I do find it useful, so I will use these analogies in the next few posts.

But what is a volt? Easy. One joule per coulomb, duh. It is also one watt per ampere. I could go on like this, but I won't.

I'll leave it there for now. Next topic will be current (I).