Electronics 101 - Part 1

Author: Matt Jason H
Published on: 20-10-2003
Views: 36013


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Introduction

About the electronics guides

In this series of guides I'll be introducing you to the concepts and practicalities of electronics, and how to use this essential and rewarding skill to add a little something special to your PC. Each part will introduce a few concepts and then a practical project or skill that demonstrates these.

In this edition I'm going to take you through the three most basic and important electronics concepts (Voltage, Current and Resistance) and the relationships between them. In the practical section I'm going to show you how to check and measure Voltage, Current and Resistance with a multimeter.

Theory

The concepts we'll be looking at

I remember in my childhood the amazement I felt watching my Amstrad Personal Computer start up for the first time, how this strange rectangular block of plastic, its innards littered with silicon and metal strips, could possibly be able to calculate things, store data, even play games! The fascination is still with me and, as I've watched technology develop at such a staggering pace, it is stronger than ever. So what is this mysterious invisible force that flows through a computer that lets you read this guide?: Electricity.

Although we really do take it for granted, electricity is an amazing thing but its also something that can be a difficult concept for people to grasp. It needn't be.

To understand electronics you need to know about three fundamental concepts: Voltage, Current and Resistance. Although there are literally hundreds of (often flawed) analogies out there I think by far the best way of explaining it is to actually look at what electricity is.

Electricity is an atomic phenomenon, it occurs when electrons move through an electrically conductive material. Electrons are one of three particles that make up atoms and are small packets of charge, this idea we shall call our Atomic Model. Electricity has three properties which we have already mentioned:

Voltage: This is much more appropriately called potential difference. In our atomic model it is the force that pushes or pulls the electrons through the wire. Voltage can either be positive (+), neutral or negative (-) and is measured in, you guessed it, Volts. To calculate voltage simply subtract the highest voltage in the circuit (or the most positive) from the smallest (or most negative). Some common examples: 9V-0V=9V, 12V-5V=7V, 12V-(-12V)=24V, etc.

Current: In our atomic model this is simply the flow of electrons through a conductor. It is measured is Amperes or Amps and expressed (in equations) not as 'C' like you would expect but as 'I'. Current is what give electricity its kick, I've had 20,000V passed through my body, it tickled; this is because it had virtually no current behind it.

Resistance: This is simply any resistance posed to the movement of the electrons in a circuit, this will reduce the voltage and limit the current. It is represented as 'R' and is measured in Ohms. Everything has a resistance, resistors (of course) are easy ways to lower the voltage/current. Remember, even wire has a resistance but we tend to ignore this because it is so small.

A diagram helping to explain the Atomic Model and Resistance. The black dots are atoms, blue are free electrons, the thinner middle section provides resistance which reduces the movement of electrons. Its important to remember that the movement of electrons before this resistance will also be slowed.

Now that we know about what Voltage, Current and Resistance is, we need to know how they are related to each other. This is explained with a really easy formula called Ohm's Law which states that Voltage = Current x Resistance (V=IR).

Ohm's Law is often remembered as a triangle. Simply cover up the letter representing what you want to find and use the equation it shows.

Ohm's Law is used a lot in electronics so lets do some examples...

1) A component is using 0.1amps of current and has a resistance of 120 Ohms, what is the voltage across it?: V=IR so V=0.1*120 =12volts

2) A component has 24volts running through it and has a resistance of 10Ohms, how much current is it drawing?: I=V/R so I=24/10 =2.4amps

3) A component has 12volts across it and is using 3amps of current, what is its resistance?: R=V/I so R=12/3 =4ohms

Now lets move on to some practical work...