# Weird equation on resistivity

1. Jan 18, 2010

### Deliria

This is a suggested relationship between L/R and L

L/R = kl + A/P

P is the resistivity, A is the cross-sectional area and k is the constant for the circuit

Using the value of the y-intercept find a value for P with the appropriate unit

The graph of L/R against L had the intercept of 9 but I have no idea where that fits in. All I know is the answer must be in Ohms

How do I calculate P?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 18, 2010

### rock.freak667

L/R = kl + A/P

is in the form Y=MX+C

where C=A/p

from a graph of Y vs X, how would you find C?

3. Jan 18, 2010

### mgb_phys

If the graph of L/R (y) against L (x) has an intercept of 9, you mean it crosses the y axis (where x=0) at 9
Therefore 9 = 0 + A/P, so A/P is 9, from the intercept we don't have any info about the slope 'k'

From this you can't separate resistivity and A - you could have a very narrow gold wire (low P) or a thick carbon (high P) one with the same resistance, ie the same P/A

4. Jan 18, 2010

### Deliria

Yes it crosses the y axis at 9.