I've got 9.6*10^-3, I've been dividing the area of the graphite (using its diameter- pieR^2) by the gardient of a graph, which is resistance times length, i believe i used length as X axis and Resiatance as Y in the graph. I really just need to know could 9.6*10^-3 be right and if not how do you work out the resistivity of graphite.....sorry for reposting
2007-03-11 01:09:04 · 3 answers · asked by Mark 2 in Science & Mathematics ➔ Physics
My gut feeling is that your answer is about a thousand times too big. I'd expect something * 10^-6. But then again, graphite is peculiar stuff!
resistance = resistivity * length / area
rearranging,
resistivity = area * resistance / length
On your graph, plotted the way you indicate, the gradient = resistance / length so I would expect you to multiply the area by the gradient to get the resistivity.
IF you had plotted your graph the other way round, with resistance as the X axis and length as the Y axis then the resistivity WOULD be worked out by dividing the area by the gradient.
Think back to the experiment: the thing that you set or change is always plotted on the X axis and the thing that results from that setting (that you measure) is plotted on the Y axis.
Hope that helps.
2007-03-11 01:47:28 · answer #1 · answered by lunchtime_browser 7 · 0⤊ 0⤋
Your almost right,. however to find the resistivity using the method you have described, requires some very accurate measurements. Remember resistivity is normally quoted in meters. and resistivity =resistance in ohms & cross sectional area of conductor divided by length. = ohms*meter*meter/meter
A conductor with a c.s.a. 1m^2 will have a very small resistance. normally ohms *10^-6. Get your units right.
hope this helps.
2007-03-13 05:49:15 · answer #2 · answered by mad_jim 3 · 0⤊ 0⤋
http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=4351759
2007-03-11 09:16:36 · answer #3 · answered by ♥shushin♥ 6 · 0⤊ 0⤋