# Thread: Ohm's Law and Resistor Band Chart (with calculator)

1. ## Ohm's Law and Resistor Band Chart (with calculator)

I was just cruising around and was surprised that I couldn't find this info posted anywhere ... covers a more technical end of micro-electronics and I couldn't really find a forum that actually FIT for this info to go other than misc topics.

This is more of a "tool" than anything, but it should help you in determining exactly how much resistance you will need to power those awesome crystal chamber LED's or accent LED's if you're broke like me and don't have a board with built-in resistance!

The formulas of Ohm's Law
Ohm's Law can be rewritten in three ways for calculating current, resistance, and voltage.
If a current I should flow through a resistor R, the voltage V can be calculated.
V = R × I
If there is a voltage V across a resistor R, a current I flows through it. I can be calculated.
I = V / R
If a current I flows through a resistor, and there is a voltage V across the resistor R can be calculated.
R = V / I

Calculator can be found here:
http://www.the12volt.com/ohm/ohmslawcalculators.asp
*Calculator page updated, courtesy of Azmaria and Google

Determining the values of your Carbon Film Resistors:

The last band of the resistor is almost always going to be either Gold or Silver, and so you can determine the direction that you should start reading from by this.

First and second colour bands:

• Black = 0
• Brown = 1
• Red = 2
• Orange = 3
• Yellow = 4
• Green = 5
• Blue = 6
• Violet = 7
• Gray = 8
• White = 9

Each band represents a digit, and so a Resistor with a Brown and then Black band would equal a value of 10. A White and then Blue band would equal a value of 96.

The Third colour band:

• Black: x1
• Brown: x10
• Red: x100
• Orange: x1K (k = 1,000 ... 1K = 1000)
• Yellow: x10K
• Green: x100K
• Blue: x1 meg
• Silver: /100
• Gold: /10

The Fourth colour band (Represents % Tolerance):

• Gold = 5%
• Silver = 10%
• None = 20%

Example Resistor: Orange, Blue, Red, Gold
3 and 6 (36) x 100 = 3600 ohms -5%

2. I know the formulae are posted in a few places, but I don't remember if the color code is.

Though people can always Google it.

But now they won't have to.

3. Thanks for the post... informative.. and organized in one area.

maybe a sticky? since the other post is hard to find then?

4. (lol) it is here.. somewhere as Ive seen it before(possibly long ago) or buried in the middle or back of some posting, this is great to push it to the top and I for one applaud the post because since you didnt find something(meaning even though its here its not easy enough to find), you used your google-fu and you actually added it... (<-very good move!!).

+1 xL (this really should be cleaned up, locked and made a sticky somewhere.. its just so basic)

EDIT!: I will attempt to find the ohms law post today

EDIT!2: Here are the 2 most important but I know there are others... Anyway these are both good reads and should be helpful for those who need some clarification
http://forums.thecustomsabershop.com...highlight=ohms

http://forums.thecustomsabershop.com...?9360-Ohms-law!

5. Stickied and moved to General Hilt Building section.

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