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.

27. Suppose that the sample of Material Y is included in an electrical circuit, as diagrammed below.

Based on Figure 1 and Table 1, if the sample is kept at 81 K, will the sample generate any heat as a result of the electrical current flowing through the sample ?

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

Refer to table 1, the temperature is 81 K, the voltage is 6.25 mV; corresponding to figure 1, the resistance of Y is still 0 at 6.25 mV, so no heat will be generated