Really Understanding Resistance in Parallel Circuits

2011 April 18
by roma

Yesterday, I happened upon furryelephant.com, a site with the best explanation of electricity concepts I've encountered yet. I was searching for explanations about short-circuits and happened upon the furryelephant.com diagram. Needless to say, I purchased a 3-day subscription and have been going through the electricity course from the beginning today.

This site is effective because it couples visuals with succinct but very carefully-phrased explanations. The user sees easy-to-understand diagrams with concepts described in detail. Common misconceptions and subtle points are also addressed. It's also clever in switching the brain by incorporating games throughout the lessons. It is fun and instills confidence in the student! I'm very excited that I've been able to find a method that (I hope!) will resolve the fine-point misunderstandings I have about electricity.

In examining the short-circuit diagram on this site, I realized the implication of the unusual effect of adding a resistance in a parallel circuit. Usually, if we add a component that makes it more difficult for a substance to flow, the total resistance will increase and the flow of the substance will decrease.

However, the opposite happens with electricity. In a parallel circuit, the addition of a new resistor will increase the total current. The majority of the current will go through the circuit with the newly-added lower resistance. According to Ohm's Law, a greater current is accompanied by a lower resistance. Imagine we have a large resistance. Picture charge as water in a tank. Picture the large resistance to be a large-diameter (low resistance) hole in the pool. Now imagine we add a smaller resistance in parallel to the large resistance. Picture the new resistor as a small-diameter hole (large resistance) in the pool. The total resistance will be a little bit less than the resistance of the small resistor.

No comments yet

Leave a Reply

Note: You can use basic XHTML in your comments. Your email address will never be published.

Subscribe to this comment feed via RSS