LAST MODIFIED:
First comes the simple answer. If the demand exists we will provide a complex answer to impedance later.
Now here comes one of the most confusing aspects of electronics - which I will de-mystify by taking an extremely casual approach, so what's new!. I have known electronic enthusiasts who still couldn't even mentally visualise the concept even after 25 years.
I'll keep it dead simple, very inelegant but dead simple and give all the purists heart palpitations. I bet you walk away with a better understanding though.
If you need to know the technical answer for impedance and you should, then consult one of the must read texts I will have suggested elsewhere.
Assume you have available these 4 items on your bench:
(a) A series of eight fresh AA type 1.5 volt cells to create a total of 12 volts supply.
(b) A 12 volt heavy duty automotive battery - fully charged.
(c) a small 12v bulb (globe) of very, very low wattage. and;
(d) a very high wattage automotive high-beam headlight.
Now if we connect the extremely low wattage bulb to the series string of AA cells we would expect all to work well. Similarly if we connect the high wattage, high-beam headlight to the heavy duty automotive battery all will be well. Well for a time anyway. Both of these sets are "sort"of matched together. Light duty to light duty and heavy duty to heavy duty.
Now what do you think would happen if we connect the high beam headlightto the series AA cells and conversely the low wattage bulb to the automotive battery?.
In the first case we could imagine the high beam headlight would quickly trash our little tiny AA cells. In the second case our min-wattage bulb would glow quite happily at its rated wattage for quite a long time. Why?, therein lies my expanation of impedance. Consider it!
The heavy duty battery is capable of delivering relatively large amounts of power but the series string is capable of delivering only relatively minimal power. The first is a low impedance sourceand the other, in comparison is a relatively high impedance source.
On the other hand the high beam headlight is capable of consuming relatively large amounts of power but the minature bulb is capable of consuming only minimal amounts of power.
Again the first is a low impedance load and the other is high impedance load. If you're keen to apply ohms law you will discover why, research it through the text books.
Meanwhile take a well deserved coffee or tea break now and think it over. Me?, I'll just have another beer while I'm waiting for you.
Good break?. If you were paying attention you would now be able to understand an analogy - a particularly rough but effective one;
Imagine a tiny caterpiller chewing on a large blade of grass - no problem plenty to eat there. Now on the other hand imagine a poor cow stuck in a desert with only one similar blade of grass available to eat. I hope you have some better understanding now.
The term impedance is a general expression which can be applied to any electrical entity which impedes the flow of current. Thus this expression could be used to denote a resistance, a pure reactance, or as is most likely in the real world, a complex combination of both reactance and resistance.
Don't get overly concerned if you're a bit confused by that statement at the moment. However this does then lead us on to "Q".
A reader wrote to me and suggested:
Hi Ian,
Thanks for the great site. I find it absolutely invaluable. It's rare to find find such high quality, free information.
I finally got the concept of impedance matching through my head. Here is a point that you might add to you discussion on impedance and the lightbulb/battery analogy:
When mismatched, neither system will deliver its designed light output. The high current bulb will deliver very little light energy when powered by the low current batteries. The low current bulb will only deliver a fraction of the light energy that the high current battery is capable of deliving. But, match the sources to the loads, and both systems run at 100% efficiency!
BOOK - A Practical Introduction to Impedance Matching by Robert L. Thomas
1. capacitance
2. inductance
3. "Q"
4. reactance
5. resistance
NEW! - How to link directly to this page
Want to create a page link to me from your site? It couldn't be easier. No HTML knowledge required; even the technophobes can do it. All you need to do is copy and paste, the following code. All links are greatly appreciated; I sincerely thank you for your support.
Copy and paste the following code for a text link:
and it should appear like this:
<a
href="https://www.electronics-tutorials.com/basics/impedance.htm" target="_top">visit Ian Purdie VK2TIP's "Impedance" Page</a>
visit Ian Purdie VK2TIP's "Impedance" Page
the author Ian C. Purdie, VK2TIP of www.electronics-tutorials.com asserts the moral right to
be identified as the author of this web site and all contents herein. Copyright © 2000, all rights reserved. See copying and links.
These electronic tutorials are provided for individual private use and the author assumes no liability whatsoever for the application, use, misuse, of any of these projects or electronics tutorials that may result in the direct or indirect damage or loss that comes from these projects or tutorials. All materials are provided for free private and public use.
Commercial use prohibited without prior written permission from www.electronics-tutorials.com.
Copyright © 2000, all rights reserved. URL - https://www.electronics-tutorials.com/basics/impedance.htm
Updated 15th May, 2000