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Chapter 25, Problem 25.79PP

BIO SPIDERWEB CONDUCTIVITY. 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:

Chapter 25, Problem 25.79PP, BIO SPIDERWEB CONDUCTIVITY. Some types of spiders build webs that consist of threads made of dry

*Based on F. Vollrath and D. Edmonds. “Consequences of electrical conductivity in an orb spider’s capture web.” Natunvissenschaften (100:12. December 2013, pp. 1163-69).

25.79 What is the best explanation for the behavior exhibited in the data? (a) Longer threads can carry more current than shorter threads do 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.

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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…
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Chapter 25 Solutions

University Physics with Modern Physics, Books a la Carte Edition; Modified MasteringPhysics with Pearson eText -- ValuePack Access Card -- for ... eText -- Valuepack Access Card (14th Edition)

Ch. 25 - When is a 1.5-V AAA battery not actually a 1.5-V...Ch. 25 - Can the potential difference between the terminals...Ch. 25 - A rule of thumb used to determine the internal...Ch. 25 - Batteries are always labeled with their emf; for...Ch. 25 - We have seen that a coulomb is an enormous amount...Ch. 25 - Electrons in an electric circuit pass through a...Ch. 25 - Temperature coefficients of resistivity are given...Ch. 25 - Which of the graphs in Fig. Q25.12 best...Ch. 25 - Why does an electric light bulb nearly always burn...Ch. 25 - A light bulb glows because it has resistance. The...Ch. 25 - (See Discussion Question Q25.14.) An ideal ammeter...Ch. 25 - (See Discussion Question Q25.14.) Will a light...Ch. 25 - The energy that can be extracted from a storage...Ch. 25 - Eight flashlight batteries in series have an cmf...Ch. 25 - Small aircraft often have 24-V electrical systems...Ch. 25 - Long-distance, electric-power, transmission lines...Ch. 25 - Ordinary household electric lines in North America...Ch. 25 - A fuse is a device designed to break a circuit,...Ch. 25 - High-voltage power supplies are sometimes designed...Ch. 25 - The text states that good thermal conductors are...Ch. 25 - Lightning Strikes. During lightning strikes from a...Ch. 25 - A silver wire 2.6 mm in diameter transfers a...Ch. 25 - A 5.00-A current runs through a 12-gauge copper...Ch. 25 - An 18-gauge copper wire (diameter 1.02 mm) carries...Ch. 25 - Copper has 8.5 1028 free electrons per cubic...Ch. 25 - Prob. 25.6ECh. 25 - CALC The current in a wire varies with time...Ch. 25 - Current passes through a solution of sodium...Ch. 25 - BIO Transmission of Nerve Impulses. Nerve cells...Ch. 25 - (a) At room temperature, what is the strength of...Ch. 25 - A 1.50-m cylindrical rod of diameter 0.500 cm is...Ch. 25 - A copper wire has a square cross section 2.3 mm on...Ch. 25 - Prob. 25.13ECh. 25 - Prob. 25.14ECh. 25 - A cylindrical tungsten filament 15.0 cm long with...Ch. 25 - A ductile metal wire has resistance R. What will...Ch. 25 - Prob. 25.17ECh. 25 - Prob. 25.18ECh. 25 - Prob. 25.19ECh. 25 - Prob. 25.20ECh. 25 - A current-carrying gold wire has diameter 0.84 mm....Ch. 25 - A hollow aluminum cylinder is 2.50 m long and has...Ch. 25 - Prob. 25.23ECh. 25 - A carbon resistor is to be used as a thermometer....Ch. 25 - A copper transmission cable 100 km long and 10.0...Ch. 25 - Consider the circuit shown in Fig. E25.26. The...Ch. 25 - An ideal voltmeter V is connected to a 2.0-11...Ch. 25 - An idealized ammeter is connected to a battery as...Ch. 25 - When switch S in Fig. E25.29 is open, the...Ch. 25 - The circuit shown in Fig. E25.30 contains two...Ch. 25 - In the circuit shown in Fig. E25.30, the 16.0-V...Ch. 25 - In the circuit of Fig. E25.30, the 5.0- resistor...Ch. 25 - The circuit shown in Fig. E25.33 contains two...Ch. 25 - When a resistor with resistance R is connected to...Ch. 25 - Light Bulbs. The power rating of a light bulb...Ch. 25 - If a 75-W" bulb (see Problem 25.35) is connected...Ch. 25 - European Light Bulb. In Europe the standard...Ch. 25 - A battery-powered global positioning system (GPS)...Ch. 25 - Consider the circuit of Fig. E25.30. (a) What is...Ch. 25 - BIO Electric Eels. Electric eels generate electric...Ch. 25 - BIO Treatment of Heart Failure. A heart...Ch. 25 - The battery for a certain cell phone is rated at...Ch. 25 - Prob. 25.43ECh. 25 - An idealized voltmeter is connected across the...Ch. 25 - A 25.0- bulb is connected across the terminals of...Ch. 25 - A typical small flashlight contains two batteries,...Ch. 25 - In the circuit in Fig. E25.47, find (a) the rate...Ch. 25 - A 540-W electric heater is designed to operate...Ch. 25 - Prob. 25.49ECh. 25 - In an ionic solution, a current consists of Ca2+...Ch. 25 - An electrical conductor designed to carry large...Ch. 25 - An overhead transmission cable for electrical...Ch. 25 - On your first day at work as an electrical...Ch. 25 - A 2.0-m length of wire is made by welding the end...Ch. 25 - A 3.00-m length of copper wire at 20 C has a...Ch. 25 - A heating clement made of tungsten wire is...Ch. 25 - CP BIO Struck by Lightning. Lightning strikes can...Ch. 25 - A resistor with resistance R is connected to a...Ch. 25 - CALC A material of resistivity is formed into a...Ch. 25 - CALC The region between two concentric conducting...Ch. 25 - The potential difference across the terminals of a...Ch. 25 - (a) What is the potential difference Vad in the...Ch. 25 - BIO The average bulk resistivity of the human body...Ch. 25 - BIO A person with body resistance between his...Ch. 25 - A typical cost for electrical power is 0,120 per...Ch. 25 - In the circuit shown in Fig. P25.66, R is a...Ch. 25 - A Nonideal Ammeter. Unlike the idealized ammeter...Ch. 25 - A cylindrical copper cable 1.50 km long is...Ch. 25 - CALC A 1.50-m cylinder of radius 1.10 cm is made...Ch. 25 - Compact Fluorescent Bulbs. Compact fluorescent...Ch. 25 - Prob. 25.71PCh. 25 - CP Consider the circuit shown in Fig. P25.72. The...Ch. 25 - CP Consider the circuit shown in Fig. P25.73. The...Ch. 25 - DATA An external resistor R is connected between...Ch. 25 - DATA The voltage drop Vab across each of resistors...Ch. 25 - DATA According to the U.S. National Electrical...Ch. 25 - Prob. 25.77CPCh. 25 - An external resistor with resistance R is...Ch. 25 - BIO SPIDERWEB CONDUCTIVITY. Some types of spiders...Ch. 25 - BIO SPIDERWEB CONDUCTIVITY. Some types of spiders...Ch. 25 - BIO SPIDERWEB CONDUCTIVITY. Some types of spiders...Ch. 25 - BIO SPIDERWEB CONDUCTIVITY. Some types of spiders...
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