a 99% pure copper wire has resistance of 0.1 ohm at 0.1 K and 20 ohm at 300K. for 100% pure copper wire of same size . what is the estimated resistance at 0.1K and 300K.a. ~0 and 19.9b. ~0 and 20.1c. 0.1 and 19.9d. 0.1 and 20.1i dont get this one, please help me..
The temperature coefficient of 100 % pure copper is required to estimate the resistances at these temperatures.
Keep in mind you're asked to estimate, so you only need to come to a logical decision: All things otherwise kept equal, the pure copper conducts better than the alloy. So, each resistance should be less by a scalar value, so answers b and d are eliminated because 20.1 > 20. 19.9 / 20 = .995 x / .1 = .995 ==> x = .0995 ~ .1 The answer is c. Annealed copper: 5.80 × 107 siemens per meter (58.0 MS/m). This is N2 copper, or .99 = 99% It works out to 1.7241x10^-8 ohm-meter To make things easier, the IACS is based on this value. So this is 100% of the IACS (International Annealed Copper Standard) For N7 copper, .9999999 = 99.99999% This is considered nearly pure and the IACS value is 103% So just take 97% of the values you currently have and you .097 and 19.42 ohms.
