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 shown in the table:

(a) What is the best explanation for the behavior exhibited in the data?

(b) If the conductivity of the thread results from the aqueous coating only, how does the cross-sectional area of the coating compare when the thread is 13 mm long versus the starting length of 5 mm? Assume that the resistivity of the coating remains constant, and the coating is uniform along the thread.

(c) What is the maximum current that flows in the thread during this experiment if the voltage source is a 9-V battery?

(d) In another experiment, a piece of the web is suspended so that it can move freely. When either a positively charged object or a negatively charged object is brought near the web, the thread is observed to move toward the charged object. What is the best interpretation of this observation?
Transcribed Image Text: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 shown in the table: Resistance of thread (10⁹2) 9 19 41 63 102 76 50 24 Length of thread (mm) 5 7 9 11 13 9 7 5 (a) What is the best explanation for the behavior exhibited in the data? (b) (b) If the conductivity of the thread results from the aqueous coating only, how does the cross- sectional area of the coating compare when the thread is 13 mm long versus the starting length of 5 mm? Assume that the resistivity of the coating remains constant, and the coating is uniform along the thread. (c) What is the maximum current that flows in the thread during this experiment if the voltage source is a 9-V battery? (d) In another experiment, a piece of the web is suspended so that it can move freely. When either a positively charged object or a negatively charged object is brought near the web, the thread is observed to move toward the charged object. What is the best interpretation of this observation?

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 shown in the table:

(a) What is the best explanation for the behavior exhibited in the data?

(b) If the conductivity of the thread results from the aqueous coating only, how does the cross-sectional area of the coating compare when the thread is 13 mm long versus the starting length of 5 mm? Assume that the resistivity of the coating remains constant, and the coating is uniform along the thread.

(c) What is the maximum current that flows in the thread during this experiment if the voltage source is a 9-V battery?

(d) In another experiment, a piece of the web is suspended so that it can move freely. When either a positively charged object or a negatively charged object is brought near the web, the thread is observed to move toward the charged object. What is the best interpretation of this observation?

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 shown in the table:
Resistance of thread (10⁹2)
9 19
41
63 102
76
50
24
Length of thread (mm)
5
7
9
11
13
9
7
5
(a) What is the best explanation for the behavior exhibited in the data?
(b) (b) If the conductivity of the thread results from the aqueous coating only, how does the cross-
sectional area of the coating compare when the thread is 13 mm long versus the starting length
of 5 mm? Assume that the resistivity of the coating remains constant, and the coating is uniform
along the thread.
(c) What is the maximum current that flows in the thread during this experiment if the voltage
source is a 9-V battery?
(d) In another experiment, a piece of the web is suspended so that it can move freely. When either
a positively charged object or a negatively charged object is brought near the web, the thread is
observed to move toward the charged object. What is the best interpretation of this observation?

Accepted Answer

a. We know, resistance depends on the length.
To be specific, with increase of the length of thread,…