Understanding Nichrome Resistivity: Exploring Resistance in a Physics Lab

[ilovephysics]

im doing a lab in physics where we measure the resistance of nichrome at different length intervals, when we plot the points and draw a line of best fit the line does NOT go through the origin, we are supposed to explain why but i have no idea why that is. can anyone help? thanks

 

[Bystander]

2, 3, or 4 wire measurement?

 

[ilovephysics]

umm i don't know we were not told anything about wire measurement..we did however calculate the resistivity, but its in my lab book which we are not allowed to take out of the lab.. the slope of my resistance vs length graph was 0.007 ohm/cm i think but i don't remember the cross sectional area to compute the resisitivity, can u still help me on the problem without it?

 

[Bystander]

That was a hint for you to think about the method of measurement. I misjudged the level of the lab. My bad.

How did you go about measuring the resistances? We should be able to work from that if you can recall the steps you went through for determining length and resistance for each point.

 

[brewnog]

Think what you're actually measuring the resistance of. I remember doing this lab, back in the day!

 

[ilovephysics]

we used a multimeter and a set of calipers to measure length...so we would put the red at our 0 and 10cm away we put our black and read the resistance, and then we would go 10cm further and take the reading of that

brewnog: arent we measuring the resistance of the metal nichrome for the given length?

 

[drpizza]

I hate to bump an old thread, but my students ran into the same question (and found this thread while trying to figure it out.) Since it's a common lab, I wanted to add in one thing that was somewhat suggested by Bystander: with your multimeter, did you attempt to measure the resistance with no nichrome at all? i.e. the resistance from one probe to the other probe? Is it zero? (On the particular brand that I use in the classroom, it is not zero; ours start with a resistance of around 0.7 ohms, which I assume is due to the wire in the probes, oxidation on the surfaces where the probes connect, etc.)