Equation of resistance

1. Apr 7, 2012

sreerajt

Voltage(V) is proportional to current(I). And so V=(a constant)*I. That constant is known as resistance(R), where R=V/I. Why can't we write that I proportional to V and then write R=I/V??

2. Apr 7, 2012

3. Apr 8, 2012

Staff: Mentor

We write G=I/V
and the units of G used to be known as mhos (that's Ohms spelled backwards) with symbol an upsidedown Ω (omega).

Nowadays, the units have been renamed an uninteresting "siemens".

4. Apr 8, 2012

Sefrez

Because that is not the reality? I know VR != I. If that were the case, current would increase with resistance. Which completely disagrees with our current definition of resistance!

EDIT:
Oh, I misinterpreted your post. Well, yes, of course you could. But R would be a different quantity, as the right side of the equation implies.

Last edited: Apr 8, 2012
5. Apr 12, 2012

sreerajt

Could you please make it clear???

6. Apr 12, 2012

f95toli

Resistance (R) is DEFINED to be what it is. There is no "reason" for it, it is just a convention.

And again, the quantity I/V already has a name of its own: conductance (G), which has the units of Siemens.

7. Apr 12, 2012

sophiecentaur

I think you means 1/R.

Remember: R is 'how hard'
and G is 'how easy'.

8. Apr 12, 2012