A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of E → in the copper; (d) the magnitude of E → in the silver; (e) the potential difference between the ends of the silver section of wire?
A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of E → in the copper; (d) the magnitude of E → in the silver; (e) the potential difference between the ends of the silver section of wire?
A 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are as given in Table 25.1. A potential difference of 9.0 V is maintained between the ends of the 2.0-m composite wire. What is (a) the current in the copper section; (b) the current in the silver section: (c) the magnitude of
E
→
in the copper; (d) the magnitude of
E
→
in the silver; (e) the potential difference between the ends of the silver section of wire?
In a physics project, you need a wire to electrically heat a cryostat. You decide to create one with materials you have lying around. You find a 29.0-g piece of copper. The resistivity of copper is 1.68 x 10-8 Ω.m, and its density is 8.9 g/cm3. You will need to use all of your copper to create a solid cylindrical wire that has a total resistance of 0.75 Ω.Determine how long your wire will be, and what its diameter will be.
A 60 W lightbulb has a resistance of 240 Ω. At the operating temperature of the tungsten filament, its resistivity is approximately 5.0 x 10-7 Ω • m. If the wire used to make the filament is 0.040 mm in diameter (a typical value).
As described above the length of a 60 W, 240 Ω lightbulb filament was calculated to be 60 cm.a. If the potential difference across the filament is 120 V, what is the strength of the electric field inside the filament?b. Suppose the length of the bulb’s filament were doubled without changing its diameter or the potential difference across it. What would the electric field strength be in this case?c. Remembering that the current in the filament is proportional to the electric field, what is the current in the filament following the doubling of its length?d. What is the resistance of the filament following the doubling of its length?
A heating element is made by maintaining a potential
difference of 75.0 V across the length of a Nichrome wire that
has a 2.60 x 10-6 m² cross section. Nichrome has a resistivity
of 5.00 x 10-7 2•m. If the element dissipates 5000 W, what is
its length? Give your answer in cm.
Chapter 25 Solutions
University Physics with Modern Physics (14th Edition)
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