What is the relationship between resistivity and the Ohm meter?

[davenn]

I just need a clarification, I have been through a dozen www sites and cannot find an answer

they show how resistivity is worked out eg ...

E/J = ρ

As you already read, ρ is the symbol for resistivity. E is the electric field and has units of Volts per meter (V/m). J is the current density and has units of amps per meter squared (A/m2). The electric field is calculated by dividing the Voltage by the length, l, that voltage is applied.

E=V/l

The current density is calculated by the equation below

J=I/A

I is the current and is divided by the cross sectional area, A, over which the current flows.

the Ohm meter is usually shown with a "dot" between Ohm and metre
Is this the same as Ohm times metre ? or Ohms per metre or something else?

I would have thought that Ohms per metre would be Ohms/metre ?

cheers
Dave

 

[Drakkith]

I don't think it's ohm x meter, as it doesn't make sense that way. It looks to me like it's just convention based on the units used to derive it.

 

[milesyoung]

It's ohm x meter, otherwise the dimensions of the units wouldn't make sense for your first equation, i.e:

E/J [V/m/(A/m^2) = V/A*m = Ω*m]

 

[Drakkith]

Hmm. Guess I must have misunderstood the math. Whoops.

 

[davenn]

That's OK Drak you probably still had a better grasp than me

thanks milesyoung

appreciate the clarification. It was something that wasn't taught in my electronics classes many years ago

and if I was ... refer to my signature

Dave