Passage V

A material is a superconductor (its electrical resistance, R, is zero) if its temperature, T, is lower than its critical temperature, Tc.

Students measured R and T for both a sample of Material X and a sample of Material Y while, each sample was cooled. They used an ohmmeter to measure R (in ohms) and a thermocouple to measure T. The thermocouple displayed the result of each measurement of T as a voltage (in millivolts, mV). Accordingly, the students plotted R versus voltage (see Figure 1). To convert voltage in mV to T in kelvins (K), they used Table 1.

Figure and table adapted from "instruction Manual for Superconductor Demonstrations." @1992 by Colorado Superconductor, Inc.

26. Based on Figure 1 and Table 1, Tc for Material Y is most likely closest to which of the following?

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

Go back to the first paragraph of the article to find the definition of TC: When the temperature of the material is lower than TC, the material is a superconductor.

Corresponding to figure 1, when the abscissa is greater than or equal to 5.5 mV, the resistance of Y is 0.

Go back to table1, the closest to 5.5 mV is 5.52 mV, corresponding to a temperature of 100 K