Finding resistivity experimentally

[nokia8650]

See: http://img229.imageshack.us/img229/5353/cirlm2.th.jpg

L is varied by moving the crocodile clips along the wire.

Am I right in thinking that the current flowing will remain the same irrespective of the length?

My reasoning:

rho=AR/L
R=V/I

sub and rearrange to give:

I=AV/L(rho)

As L increases, V increases by the same proportion. A and rho remain constant. Thus, I is constant.

Thanks

 

[Nick89]

What is L? You did not even specify it in the image...

I am going to assume you are changing the position of the 'arrow' on the black wire, effectively measuring a different voltage?

Then I believe yes, theoretically, the current will remain the same since an ideal voltage meter (what's the word?) has an infinite resistance. (So no current will flow through the 'shortcut' with the voltage meter)

In practice, it will obviously have a finite (but very large) resistance and the current might change a little, but this will probably be very small.

 

[nokia8650]

Hi, sorry for not defining the symbols. L was the length, and thanks, as you answered my question despite me being unclear!