The Resistor FAQ

[Keshetisrael]

The Resistor F.A.Q

Resistors are a very important part of a Circuit. We all know that every little bit counts! So.. here's as much as you should need to know about Resistors that I know. (Mind you, I'm still learning; and in fact this is helping me to learn. Hope other's find help here!)


What's the Schematic Symbol for a Resistor?





What's the Code for all The Colored Strips on a Resistor?






Here's two Free Resistor Code Apps for help:

Electronics Assistant V4.31 & Resistor Color Coder 2.1


How can you tell, just by looking at a resistor what 'brand' it is? Or Can you?

Knowing the 'BRAND' of the Resistor isn't necessary. I would like to hear experienced Techs own loyalties on this however! So, what's the best BRAND of resistors in your opinion? (If someone Can, please do tell!)

How can you tell what 'KIND' of Resistor A resistor is? Is it a Carbon Composition, Carbon Film, Metal film, Metal oxide Or wire wound?

Metal Film:


http://www.resistorguide.com/metal-film-resistor/





I found these worth their read: http://electronics.stackexchange.com...nd-what-values

https://learn.sparkfun.com/tutorials/resistors/all

How do I know what Wattage the resistor is that I'm replacing?

The Schematics give Voltage (V) to the Resistor and you know the Resistor's Ohm Value (From color codes). So.. after you Find Current (I) (from I= V/R) then you find P (wattage) = V(squared)/R






Here's a Quote from Mariushm (BadCaps Veteran):

"Usually, [the] white/cream resistors are carbon film, blueish/green resistors used to be metallic , carbon film resistors usually have lousy temperature coefficient and larger tolerance (5-10%) High wattage resistors are wirewound usually (let's say 1w or higher).

Power dissipated in a resistor is calculated by formula IxIxR where i = current and r=resistor value and generally the recommendations are to not exceed about 70-80% of the resistor's wattage rating. 1w resistors are quite large. When in doubt, you can go with 0.5w resistors or 1w resistors instead of 0.125w or 0.25w resistors.


Here's some other Resources (on Wattage):
http://techtalk.parts-express.com/sh...wattage-rating

http://www.robogaia.com/how-to-calcu...r-wattage.html

On Resistors:

http://www.mikroe.com/old/books/keu/01.htm

What is the Electronic Industries Association (EIA) 'Preferred Values' for Resistors?

Easiest Answer is to give you this site link:

http://www.logwell.com/tech/componen...or_values.html

Any additional information that is relevant will be greatly appreciated. Please add to this Museum of Needed Electronics Information! Namaste- <><
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[mariushm]

Personally, I'd really appreciate it if you wouldn't link to that ad filled site informer.com ... it basically spams Google with tons of keyword generated URLs ... just look at https://www.google.com/search?q=site%3Ainformer.com to see what I mean. Don't condone that style of website by linking to it.

There are open source or free tools that are much more useful than a simple resistor color thing, for example I can mention Electronics Assistant : http://www.electronics2000.co.uk/


As for the other questions.. usually white/cream resistors are carbon film, blueish/green resistors used to be metalic , carbon film resistors usually have lousy temperature coefficient and larger tolerance (5-10%)
High wattage resistors are wirewound usually (let's say 1w or higher).

Power dissipated in a resistor is calculated by formula IxIxR where i = current and r=resistor value and generally the recommendations are to not exceed about 70-80% of the resistor's wattage rating.

1w resistors are quite large. When in doubt, you can go with 0.5w resistors or 1w resistors instead of 0.125w or 0.25w resistors.

[SteveNielsen]

Here's a sampling of power resistors ranging from 3 watts to 225 watts. The one on the far left is a slider type variable resistor missing the slider.

[budm]

"A typical radio shack resistor you will often see is a 2.2kohm resistor with 10% tolerance. The bands are "Red" (2), "Red" (2), "Red" (times 10^2), "Gold" +/- 10%." FYI: GOLD is 5%

[Hamie]

Can anyone tell me what watt this resistor is?

[mariushm]

White , Yellow, Black as far as I can tell : 9 4 0 = 94 x 10^0 = 94 x 1 = 94 ohm.

[Hamie]

Originally Posted by mariushm

White , Yellow, Black as far as I can tell : 9 4 0 = 94 x 10^0 = 94 x 1 = 94 ohm.

thanks for the reply but its not the ohms im looking for its the watt.
its brown black yellow gold.
so my calculations are 100k with 5% tolerance.
but its quite a big resistor so unsure of wattage! probs just going to get a 2W and hope for the best!

[SteveNielsen]

The pic is pretty blurred and can't tell what the coin is but that looks to me like a 1W 100K 5%
brown black yellow gold

[Hamie]

hi its a uk penny. your colours are correct. ill get a 1 watt aswell as the 2 watt

[SteveNielsen]

It probably won't be a problem using a 2W if it fits.

[Hamie]

cheers steve

[watchmaker]

High wattage resistors are wirewound usually (let's say 1w or higher).

2 W resistors are not all wirewound, there are many types of 2 W metal film resistors. 5 W and higher are always wirewound.

[Hamie]

Ok struggling with this resistors value?
Anyone able to help?
the pink ones.

[Hamie]

Looks like brown, black, gold, red, black.

Wasn't aware gold could be a middle band