# e=ir

Discussion in 'Homework Help' started by Debdut, Mar 11, 2012.

1. ### Debdut Thread Starter New Member

Aug 26, 2011
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E=ir how do get the formula?

Apr 5, 2008
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3. ### Debdut Thread Starter New Member

Aug 26, 2011
7
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I have seen it but thats not the proof.

Apr 5, 2008
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Nov 25, 2009
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6. ### Debdut Thread Starter New Member

Aug 26, 2011
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The wiki page that Bertus gave was somewhat helpful.But my question is different that whether e=ir has a mathematical proof or its just a experimental approximate consequence?

7. ### DerStrom8 Well-Known Member

Feb 20, 2011
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Why don't you put a simple circuit together? Get a 9 volt battery, a 1Kohm resistor, and a multimeter. First measure the exact voltage of the battery, and the exact resistance of the resistor. Then connect the resistor to the battery, in series with the multimeter (set in current mode). What current does it show? Then put the resistance and voltage into Ohm's Law (E=IR, or rearranged to get current, I=E/R). What current do you get? Is it close to what your multimeter showed?

Try this with a few different resistors, like 4.7K, 6.8K, etc. Check all of them and see if it's close. What more proof do you need?

Regards

8. ### crutschow Expert

Mar 14, 2008
21,359
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Ohm's law is an empirical (experimentally determined) relation. There is no other fundamental proof or derivation of it.

9. ### justtrying Senior Member

Mar 9, 2011
330
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if you follow DerStrom's advise, you should get a linear relationship between V and I for the data you collect. That directly verifies Ohm's Law (as long as you verify it using Ohmic devices )

10. ### Georacer Moderator

Nov 25, 2009
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Maybe the correct thinking is to say that Power is defined as Voltage*Current and then work your way through Ohm's law.

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11. ### DerStrom8 Well-Known Member

Feb 20, 2011
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That and Voltage is defined as Current*Resistance

12. ### amilton542 Active Member

Nov 13, 2010
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#12 and DerStrom8 like this.
13. ### DerStrom8 Well-Known Member

Feb 20, 2011
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Ah, this guy. I've seen him before on more than one occasion

I must say, he's good at what he does, and he sure knows his stuff!

14. ### amilton542 Active Member

Nov 13, 2010
496
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His name is Walter Louin: he used to be a nuclear physicist. I think he left MIT for X-ray Astronomy.

He has a 'moan' at the students on one of the videos over complaining about his method of delivery - I love education.

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15. ### #12 Expert

Nov 30, 2010
18,076
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The Professor at MIT? Beats my argument!

I was going to say E=IR like F=MA
They are fundamental relationships and all you have to do to get them to work is get the units right. But then, I get a headache at the idea of looking up Issac Newton's work and trying to prove F=MA

Better to leave it to the MIT Professor. Saves me all kinds of brain strain.
and a big Thank You to amilton542

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