Chapter 25: Problem 27
Two conductors of the same length and radius are connected to the same emf device. If the resistance of one is twice that of the other, to which conductor is more power delivered?
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Two cylindrical wires of identical length are made of copper and aluminum. If they carry the same current and have the same potential difference across their length, what is the ratio of their radii?
Two conducting wires have identical lengths \(L_{1}=L_{2}=L=10.0 \mathrm{~km}\) and identical circular cross sections of radius \(r_{1}=r_{2}=r=1.00 \mathrm{~mm} .\) One wire is made of steel (with resistivity \(\rho_{\text {ard }}=40.0 \cdot 10^{-8} \Omega \mathrm{m}\) ); the other is made of copper (with resistivity \(\rho_{\text {copper }}=1.68 \cdot 10^{-5} \Omega \mathrm{m}\) ). a) Calculate the ratio of the power dissipated by the two wires, \(P_{\text {copper }} / P_{\text {sted }}\) when they are connected in parallel and a potential difference of \(V=100 . V\) is applied to them. b) Based on this result, how do you explain the fact that conductors for power transmission are made of copper and not steel?
In an emergency, you need to run a radio that uses \(30.0 \mathrm{~W}\) of power when attached to a \(10.0-\mathrm{V}\) power supply. The only power supply you have access to provides \(25.0 \mathrm{kV}\), but you do have a large number of \(25.0-\Omega\) resistors. If you want the power to the radio to be as close as possible to \(30.0 \mathrm{~W}\), how many resistors should you use, and how should they be connected (in series or in parallel)?
What would happen to the drift velocity of electrons in a wire if the resistance due to collisions between the electrons and the atoms in the crystal lattice of the metal disappeared?
Which of the following wires has the largest current flowing through it? a) a 1 -m-long copper wire of diameter 1 mm connected to a 10 - \(V\) battery b) a 0.5-m-long copper wire of diameter \(0.5 \mathrm{~mm}\) connected to a 5 - \(\mathrm{V}\) battery c) a 2 -m-long copper wire of diameter 2 mm connected to a 20 - V battery d) a \(1-\mathrm{m}\) - long copper wire of diameter \(0.5 \mathrm{~mm}\) connected to a \(5 \cdot \mathrm{V}\) battery e) All of the wires have the same current flowing through them.
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