Question

Some types of spiders build webs that consist of threads made of dry silk coated with a solution of a variety of compounds. This coating leaves the threads, which are used to capture prey, hygroscopic—that is, they attract water from the atmosphere. It has been hypothesized that this aqueous coating makes the threads good electrical conductors. To test the electrical properties of coated thread, researchers placed a 5 mm length of thread between two electrical contacts. The researchers stretched the thread in 1 mm increments to more than twice its original length, and then allowed it to return to its original length, again in 1 mm increments. Some of the resistance measurements are given in the table.

Resistanc of thread (109ft) 9 19 41 63 102 76 50 24
Length of thread 5 7 9 11 13 9 7 5

What is the best explanation for the behavior exhibited in the data?
a. Longer threads can many more current than shorter threads and so make better electrical conductors.
b. The thread stops being a conductor when it is stretched to 13 mm due to breaks that occur in the thin coating.
c. As the thread is stretched, the coating thins and its resistance increases; as the thread is relaxed, the coating returns nearly to its original state.
d. The resistance of the thread increases with distance from the end of the thread.

Answer 1

c. As the thread is stretched, the coating thins and its resistance increases; as the thread is relaxed, the coating returns nearly to its original state.

Step-by-step explanation:

This is in line with the result as shown in the data.

Stretching causes the coating to thin which in turn increases the resistance of the thread (conduction drops) releasing it backs returns the thread to nearly its initial values, but due to the strain already in the thread it does not return to its original values.