CURRENT AND RESISTANCE


Ok now let's try to understand a bit more about what happens when electrons move. Take the following example: Given the diagram below, which bucket is filling up first?




Yep you're right! Bucket A will get filled up first. Now do you know why? Well it’s because the water that flows to bucket A does not have to go through so many obstacles in the pipeline to get to the bucket but for bucket B there are so many things inside the pipeline that keep bumping against the water and therefore not allowing it to reach the bucket in time. Some cloggy pipe don’t you think?

So what does this have to do with electrons and Ohm’s law? Well imagine that each drop of water in each of the pipelines was a bundle of electrons moving in a certain direction within a wire (which is represented by the pipeline). Because there are different kinds of wires like different kinds of pipelines, some types of wires resist the flow of the electrons through them because of the material that they are made up of. This is what we call Resistance. Most materials that allow electricity to pass through (known as conductors) have different degrees of resistance because they are made up of different types of materials. Thus all electrical appliances including wires have a Resistance!

Have you ever seen resistors before?  No-don't think so?  If you've ever seen a lightbulb, then you've seen a resistor. Electricians use specially constructed resistors in your house, stereo, computer, car, and other electronic equipment. The resisors are purposely used to help control the amount of current (or flow of electrons) through any circuit. Take a look at some of these resistors (below).   The color bands on each resistor are a special code that tells electricians how much resistance the resistor provides .The codes for  the symbols used below are as follows: K - represents 1000 (e.g. 47,000  ohms or 47K ohms),  % represents the tolerance level of the resistor where 2%-red, 5%-Gold, 10%-silver.





  Source: http://www.armory.com/~rstevew/Public/Tutor/resistor.gif