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# (AQA) AS Physics Voltage-Length graphs watch

1. Hi all,

In Physics, I did an experiment on calculating the resistivity of a material by altering the length of the wire.

I have calculated the gradient of the graph, however, I am not sure of what this actually tells me? My educated guess is that it is the value of (V/L), but I'm not sure.

Could someone please enlighten me on this?

Thank you very much!
2. Im not sure about this (since I did alternative to practicals) but if we look at the formulae:
1. Resistance = (resistivity of the material X length of the wire)/ cross sectional area of the wire
2. Voltage= resistance X current (V=IR)

Since you drew a graph of Voltage against length, we need voltage on one side and length on the other

V=IR
R= V/I - valid.

R= pl/A
V/I= pl/A
V= (pl X I)/A (in words, voltage = resistivity into length of the wire into the current divided by the Area)

Since y= mx + C (the gradient of a straight line)
the gradient of a Voltage-length graph should give you (pXI)/ A i.e resistivity into current divided by Area.

I hope you can understand how I got the gradient (The i and the l look very similar, sorry about that.)

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