Question about Ohms law


Old 03-10-04, 04:47 PM
Thread Starter
Join Date: Feb 2004
Location: ohio
Posts: 61
Question about Ohms law

Can somebody explain Ohms law. I think I know what it is, but would like an explanation just to be sure. Better to be safe than sorry and utterly stupid.
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Old 03-10-04, 05:40 PM
Join Date: Feb 2004
Location: So Cal
Posts: 248
Ohm's Law

Simply put, it's a formula for calculating an unknown electrical value (volts, amps or ohms) when two values are given.

Here's how it works:

I can't draw a circle here, but draw a circle on a piece of paper, divide the circle in half left to right and divide the bottom half top to bottom. Put E (volts) in the top, I (amps) in the left lower quadrant and R (ohms) in the right lower quadrant.

E (volts)
I (amps) | R (ohms)

Then just multiply or divide the two known values to get the unknown value. For example, to find ohms (Resistance) divide volts by amps. If you have a 12 volt circuit pulling 6 amps of current, you've got 2 ohms resistance.


Old 03-10-04, 06:08 PM
Desi501's Avatar
Join Date: Oct 2003
Location: Boynton Beach Florida
Posts: 2,207
I think the description of the law goes like this. It take 1 volt to push 1 amp through 1 ohm of resistance. If you know any 2 of the values, you can calculate the third.
Old 03-10-04, 06:56 PM
carguyinva's Avatar
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147
both of you gat an "A"!

desi is correct that the basis for ohm's law is that 1 volt will push one amp of current thru one ohm of resistance.

smogtek is also correct in that for practical application,
E = I x R...the circle thing works like this...if you cover the value you are searching for in the circle, you are laft with the equation to figure it out. so...E is on top and and I and R are side by side on the bottom...cover up the R and you are left with E over I...or...

R = E/I

I = E/R

just sayin the same thing another way....

ohm's law is also the basis for making your own amp shunt...a device for checking amperage draw (small ones) using a voltmeter.

let me know if you want to make one...they're inexpensive...and I'll give you the list of parts and the procedure
Old 03-10-04, 07:29 PM
Thread Starter
Join Date: Feb 2004
Location: ohio
Posts: 61
amp shunt

Yes I would like to make one instructions and parts list would be appreciated. Also some practical applications, such as which circuits to check THANKS

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