## anonymous one year ago what is mean by ohm's law

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1. MrNood

This is the very basic relationship you will need to UNDERSTAND FOR YOUSELF as you study electricity. It is useless if someone else writes it here for you. You WILL definitely need to have it in your head as a known fact as you go through your studies - it is not an option if oyu are going to make any progress. Go back to your text, your class, your books or go here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ohmlaw.html but please take the chance now to learn and UNDERSTAND this very simple relationship. Any time you spend learning this now will be repaid many times over as you learn more about physics and electric currents.

Very well said MrNood

3. Michele_Laino

the equation which models a conductor, is: $\Large {\mathbf{J}} = \sigma {\mathbf{E}}$ where J is the density current, E is the electric field, and \sigma is the conductibility of that conductor, note that that is a vector equation. Now I use the definition of J, so I multiply both sides of that equation by the cross sectional area A of our conductror, and I get: $\Large I = \sigma EA$ |dw:1432842502503:dw|

4. Michele_Laino

since E*L = V= voltage drop across our conductor, then we can write: $\Large I = \sigma EA = \sigma \frac{{ELA}}{L} = \frac{{\sigma VA}}{L} = \frac{V}{{\frac{L}{{\sigma A}}}}$

5. Michele_Laino

Now, the quantity: $\Large {\frac{L}{{\sigma A}}}$ is the electric resistance R of our conductor, so finally we can write: $\Large I = \frac{V}{R}$ namely the Ohm's law

6. Michele_Laino

oops..J is the current density, namely: $\Large JA = I$

7. MrNood

@PRIYASUKI Please do not let @Michele_Laino 's complicated explanation put you off. That was entirely unnecessary for an initial explanation The starting point you want is I = V/R Where I is the current in a DC resistor Vi s the voltage across it, and R the resistance Note = The current increase linearly as the voltage increase and decreases inversely as the resistance increases I= V/R V=IR R= V/I Just go back to this simple equation for your early studies - it will take you further than you will probably need - and will never encounter the other stuff above unless you get to some advanced electrical studies. Please just start with the basics - you WILL need them if you are going to study physics.

8. Michele_Laino

My explanation is not complicated, it is the official science @MrNood

9. MrNood

There is no 'official' science - it grows and changes with our knowledge and experience. Remember - in 'Futurama' they refer to our times as 'The Stupid Age' Your explanation is perfectly fine for the question 'explain the derivation of Ohms Law' but for someone who has asked a vey basic question it is almost certain to scare them away. Ohm 'Law' is well understood at most levels to be adequately defined as simply I=V/R

10. Michele_Laino

no, no, there exists the official science, and the Ohm's law is a result of a reasoning, so we have to explain that reasoning in order to learn that Ohm's law

11. MrNood

@Michele_Laino Is 'official science' phlogiston theory, Rutherford- bohr model of the atom, big bang theory, string theory, creationism earth air fire water, bloodletting, leeches?..... I could go on about all the 'official science' that is now seen to be only the best available at the time. It is a failing of most scientist to acknowledge that there is a high probability that they are wrong, at least in detail and possibly in concept, about everything. Have you ever studied mathematics - do you KNOW teh fundamental of the everyday maths we use ? I suspect not - but yo uuse the tools with acceptance that it is on a firm basis. MOST people on this board do NOT need to be led through the derivation of every equation they see,provided that it is given in context and at an appropriate level for their current learning.

12. rvc

The basics of Ohm's law V=IR this is what i learned when i heard it first time :) by the way @Michele_Laino your explanation is awesome but i think that the user is totally new to Ohm's law. He/She must be first familiar with the basics. @MrNood i understand you too well at the end the user has both the choices :) if he/she wants to know just the basics then he/she can refer to the short and sweet ans And if the user is much more interested then we have more knowledge :)