11:27 Whoops, m is the mass of the wire and c is the specific heat capacity of the wire, not the other way around. Silly slip up, but I thought I'd better clarify. Throughout this video, I use the unit volts per ampere. Well, volts per ampere is an equivalent unit to ohms, the derived unit of resistance. I've kept it as volts per ampere because I measured p.d. and current, so I thought it would make things clearer. The values in the table with units millivolts per ampere are equivalent to those values with units milliohms. The highest mean resistance of copper during the experiment was 77.78 milliohms, which is why the use of my ohmmeter wasn't appropriate - it didn't have a high enough resolution to be able to measure such a small resistance.
The length of wire is too short. We use copper wire in large 100m x 100m loops for electromagnetic geophysical measurements, and the resistance can be measured more easily that way, even with a resistance meter. The other way is to use a large current, as Big Clive does in this video, although he did not set out to measure the resistivity of copper, he was testing a jump starter pack! /watch?v=0tGK1nqXr28&t=708s Clive gave his result as 110uV/A From the video images I estimated the spacing of the voltage leads at L =0.2m (20cm) - this was a possible source of error. The diameter of UK 1/2" copper pipe is given as 15 mm (ext) and 13.4 (int) giving a wall cross-section area of 31.2 mm². The resistivity is RA/L then 110 uV/A x 31.2 x 10^-12 / 0.2 = 1.71 x 10^-8. (using metres for length and area) Published value for hard-drawn copper is 1.77 x 10^-8 ohm-metres, only 3% error, but the heating effect was disregarded.
11:27 Whoops, m is the mass of the wire and c is the specific heat capacity of the wire, not the other way around. Silly slip up, but I thought I'd better clarify.
Throughout this video, I use the unit volts per ampere. Well, volts per ampere is an equivalent unit to ohms, the derived unit of resistance. I've kept it as volts per ampere because I measured p.d. and current, so I thought it would make things clearer. The values in the table with units millivolts per ampere are equivalent to those values with units milliohms. The highest mean resistance of copper during the experiment was 77.78 milliohms, which is why the use of my ohmmeter wasn't appropriate - it didn't have a high enough resolution to be able to measure such a small resistance.
The length of wire is too short. We use copper wire in large 100m x 100m loops for electromagnetic geophysical measurements, and the resistance can be measured more easily that way, even with a resistance meter.
The other way is to use a large current, as Big Clive does in this video, although he did not set out to measure the resistivity of copper, he was testing a jump starter pack! /watch?v=0tGK1nqXr28&t=708s Clive gave his result as 110uV/A
From the video images I estimated the spacing of the voltage leads at L =0.2m (20cm) - this was a possible source of error.
The diameter of UK 1/2" copper pipe is given as 15 mm (ext) and 13.4 (int) giving a wall cross-section area of 31.2 mm².
The resistivity is RA/L then 110 uV/A x 31.2 x 10^-12 / 0.2 = 1.71 x 10^-8. (using metres for length and area)
Published value for hard-drawn copper is 1.77 x 10^-8 ohm-metres, only 3% error, but the heating effect was disregarded.
Did you watch the video?
@@PhysicswithKeith Yes, I did, you did a lot better than Big Clive with less than 1% error.
Thank you 🙏 I was very happy with the result