Ohms Law

The relationship between current(I), voltage(V or E), and resistance(R) was discovered by a German scientist named Georg Ohm. This relationship is named Ohms Law in his honor. Ohm found that the current in a circuit varies directly with the voltage when the resistance is constant. Ohm varied the voltage across the resistance and measured the current through it. In each case, when he divided voltage by the current, the result was the same. In short, Ohms Law, which can be stated as, "The current is directly proportional to the voltage and inversly proportional to the resistance".

Written as a mathematical expression, Ohms Law is

Resistance(R)=voltage(V)/current(I) or R=V/I

The above equation allows you to determine the value of the resistance when the voltage and the current are known.

Of course, Ohms Law can be rearranged to solve for either current or voltage. The rearranged relationships are

current(I)=voltage(V)/resistance(R) or I=V/R

and

voltage(V)=current(I)*resistance(R) or V=IR

Here is a list of equations for power, voltage, current, and resistance

Power(W)= EI, I(squared)*R, E(squared)/R

Voltage(V)= IR, P/I, (sqrt)PR

Current(I)=E/R, P/E, (sqrt)P/R

Resistance(R)= E/I, E(squared)/P, P/I(squared)

Herbymcduff

 

Here's a good artical on ohm's law.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

MOD EDIT: raybo,Please try to by polite!

 

hmmm, i dont know what makes your posts more irritating;

how you jam everything together and make it hard to read,
or how you just whine and scream at people for anything and everything.

help me out on that one. what do you think?

 

People are passionate about the things they love. (Or passionate about hating the things they hate.)

 

i always used the triangle way

_v__
I(x)R

and cover over the one you want to find

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CAPTAINCAVEMAN

 

I never understood the triangle method. It was always easier for me just to remember V=IR and use algebra which has been burned into my brain. THere is another triangle method I used though...but I forget what it was and what it was used for.

 

if you look at the bad pick i drew, with a divide being the line under v, then just cover over the one you want to find eg cover over the v in that drawing and whats left is IxR cover the I and you got V/R etc

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CAPTAINCAVEMAN

 

i dont think there is any need of some trialngular method to remember the ohm's law.probably the easiest and the simplest of all the formulae

 

i too go with him.i never understood it.its just complicating an easy thing

 

I think what he says in the triangle method is some what same as ohms law. What he meant by covering is that you write down the triangle method and just cover the one you want to find and the remaining is the formula to find it. For example if you want to find V then cover V and the rest is your formula. I think he touches the nose the other way round. Anyway thanks CAPTAIN.

 

the triangle method is how i was taught and remember it, also use a triangle for power, amps and voltage.

Its my preferred way, but im sure everyone is taught or learns it differently.

 

But I Think Ohms Law Is Not V=ir But It Is The Statement That Voltage Is Directly Proportional To Resistance Because It Is Said That Semiconductors Do Not Obey Ohms Law But Obey V=ir Can Someone Explain This

 

Semi conductors obey ohms law the same as every other material in the universe does. All materials have varying conductances at different temperatures and under various circumstances. The semi conductors popularized in electronics just do so to a significantly greater degree than 'common' materials do.

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hi sceadwian,

Semi-conductors are not conductors which do not conduct very well.

I know that I am slightly misquoting you. Sorry, just trying to stress the point.

Semiconductors have a totally different characteristic to a resistor.
Ohms law dosn't apply.

Regards
Eric