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### Topic: Resistance question (Read 2172 times)previous topic - next topic

#### funkyguy4000

#15
##### Oct 19, 2011, 12:51 am
haha okay
I was looking for my advanced physcis book from high school, it had some circuit diagrams dealing with ohms law and I could find it.
I couldn't find many practice ohms law circuits (actually i didn't find any) when I looked online.
Yea what I did was put them all in a series, probably won't do that again....at least until i understand how to do it right!
I'll certainly still have questions but I need to get some practice diagrams first and then get the stats on all of my components.
Silly china making it difficult with their components
Accelerate to 88 miles per hour.

#### funkyguy4000

#16
##### Oct 19, 2011, 02:09 am
OH! and by the way, How can you be sure the band that you are looking at is in fact the right color.  There's silver and grey, red and brown, purple and black.  sometimes i feel like the silver and grey bands are exactly the same.  And the other 2 combos look so similar its hard to tell the difference, is there a way to like know for sure?  Or does everybody just guess in the dark with the chart when they've forgotten the resistance of the mystery resistors in their bag
Accelerate to 88 miles per hour.

#### justjed

#17
##### Oct 19, 2011, 02:28 am

Or does everybody just guess in the dark

At the least, you should have a meter. I currently use a cheapo Gardner-Bender DMM I found at Lowe's for under \$10 -- saving my pennies for something better. But it does the job for simple stuff. Home Depot or Radio Shack are two other sources. You got a Fry's near you? Microcenter?
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

#### funkyguy4000

#18
##### Oct 19, 2011, 02:33 am
Oh well that would work. I think theres a home depot around here.  Theres a walmart, can i get one there?
Accelerate to 88 miles per hour.

#### justjed

#19
##### Oct 19, 2011, 02:36 am
The Wal-Mart website has a search function which will tell you whether an item is available in a store.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

#### funkyguy4000

#20
##### Oct 19, 2011, 02:40 am
derp

Well thanks!
Back to my other question, does anybody have a resource for practice circuit diagrams for Ohms Law?  I was looking but could not find any for some odd reason, maybe a fluke but i'm wondering if anybody has anything bookmarked that they could share or knows where there are some.
Accelerate to 88 miles per hour.

#### Grumpy_Mike

#21
##### Oct 19, 2011, 11:24 am
Have a look at this:-
http://www.furryelephant.com/
Lots of animated diagrams.

#### pekkaa

#22
##### Oct 19, 2011, 12:13 pm
A multimeter is a must. Until you get one, if you have at least one resistor which value you know, you can build a voltage divider with the know and an unknown resistor and read the voltage between them using the Arduino's analogRead().  Then simple calculation gives you the resistance of the unknown resistor. Btw, in addition of the Ohm's law, study also the Kirchhoff's circuit laws.

#### funkyguy4000

#23
##### Oct 20, 2011, 01:29 am
quick question, so i just recieved the pwm drivers from texas instruments and I'm unsure if i have the correct resistors.

Lets just say that I don't, and lets say the required resistance is 300 ohms.  would i be able to put 3 100 ohm resistors in a series?
Accelerate to 88 miles per hour.

#### justjed

#24
##### Oct 20, 2011, 02:15 am
Resistance in series is additive, so yes.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

#### funkyguy4000

#25
##### Oct 20, 2011, 02:58 am
WOOOT!!!!
then i have a question, where does equivalent resistence come into play.
I know that if you have a resistor that is connected to many leds, then the resistance is divided among them (i hope thats right)

but where does the equivalent resistance.
Accelerate to 88 miles per hour.

#### justjed

#26
##### Oct 20, 2011, 04:48 amLast Edit: Oct 20, 2011, 05:07 am by justjed Reason: 1

WOOOT!!!!
then i have a question, where does equivalent resistence come into play.
I know that if you have a resistor that is connected to many leds, then the resistance is divided among them (i hope thats right)

I completely don't grok that question.

ETA: The following 2 circuits are not equivalent:
Code: [Select]
`  ---\/\/\/\/--->|--->|--->|---      300 ohm  ---|---\/\/\/\/--->|---|---     |    100 ohm        |     |---\/\/\/\/--->|---|     |    100 ohm        |     |---\/\/\/\/--->|---|          100 ohm`
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

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