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(a) What are the ratios of the resistances of (a) silver and (b) aluminum wire to the resistance of copper wire $\left(R_{\mathrm{Ag}} / R_{\mathrm{Cu}} \text { and } R_{\mathrm{A}} / R_{\mathrm{Ca}}\right)$ for wires of the same length and the same diameter? (c) Which material is the best conductor, for wires of equal length and diameter?

Short Answer

Expert verified
Question: Given equal length and diameter, calculate the resistance ratios for silver and aluminum wires compared to copper wires and determine which material is the best conductor. Answer: The resistance ratios for silver and aluminum wires compared to copper wires are approximately 0.92 and 1.64, respectively. Silver is the best conductor among the three materials, followed by Copper and then Aluminum.

Step by step solution

01

Recall the resistance formula

The resistance formula can be written as: \(R = \frac{\rho * L}{A}\), where \(R\) is resistance, \(\rho\) is resistivity, \(L\) is the length of the wire, \(A\) is cross-sectional area. For our given problem, we know that the length and diameter of the wires are equal, meaning that the length \(L\) and the cross-sectional area \(A\) will remain constant in our calculations.
02

Calculate the resistance ratios for silver and aluminum wires compared to copper wires

We need to find \(R_{\mathrm{Ag}} / R_{\mathrm{Cu}}\) and \(R_{\mathrm{Al}} / R_{\mathrm{Cu}}\). We know that \(\frac{R_{1}}{R_{2}} = \frac{\rho_{1}}{\rho_{2}}\) because \(L\) and \(A\) are equal. Given the resistivities of Silver (\(\rho_{\mathrm{Ag}} = 1.59 \times 10^{-8} \,Ω \cdot m\)), Aluminum (\(\rho_{\mathrm{Al}} = 2.82 \times 10^{-8} \,Ω \cdot m\)), and Copper (\(\rho_{\mathrm{Cu}} = 1.72 \times 10^{-8} \,Ω \cdot m\)): \(R_{\mathrm{Ag}} / R_{\mathrm{Cu}} = \frac{\rho_{\mathrm{Ag}}}{\rho_{\mathrm{Cu}}} = \frac{1.59 \times 10^{-8}}{1.72 \times 10^{-8}} \approx 0.92\) \(R_{\mathrm{Al}} / R_{\mathrm{Cu}} = \frac{\rho_{\mathrm{Al}}}{\rho_{\mathrm{Cu}}} = \frac{2.82 \times 10^{-8}}{1.72 \times 10^{-8}} \approx 1.64\)
03

Find the best conductor in terms of material

We now have the resistance ratios of Silver and Aluminum compared to Copper. The best conductor is the one with the lowest resistance for the same length and diameter wires. From our calculations, we can see that Silver has the lowest resistance, with a ratio of approximately \(0.92\). Therefore, Silver is the best conductor among the three materials, followed by Copper, and finally, Aluminum.

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Most popular questions from this chapter

An ammeter with a full scale deflection for \(I=10.0 \mathrm{A}\) has an internal resistance of \(24 \Omega .\) We need to use this ammeter to measure currents up to 12.0 A. The lab instructor advises that we get a resistor and use it to protect the ammeter. (a) What size resistor do we need and how should it be connected to the ammeter, in series or in parallel? (b) How do we interpret the ammeter readings?
A 6.0 -pF capacitor is needed to construct a circuit. The only capacitors available are rated as \(9.0 \mathrm{pF} .\) How can a combination of three 9.0 -pF capacitors be assembled so that the equivalent capacitance of the combination is \(6.0 \mathrm{pF} ?\)
An aluminum wire of diameter 2.6 mm carries a current of 12 A. How long on average does it take an electron to move \(12 \mathrm{m}\) along the wire? Assume 3.5 conduction electrons per aluminum atom. The mass density of aluminum is \(2.7 \mathrm{g} / \mathrm{cm}^{3}\) and its atomic mass is $27 \mathrm{g} / \mathrm{mol}$.
A current of \(2.50 \mathrm{A}\) is carried by a copper wire of radius $1.00 \mathrm{mm} .\( If the density of the conduction electrons is \)8.47 \times 10^{28} \mathrm{m}^{-3},$ what is the drift speed of the conduction electrons?
Near Earth's surface the air contains both negative and positive ions, due to radioactivity in the soil and cosmic rays from space. As a simplified model, assume there are 600.0 singly charged positive ions per \(\mathrm{cm}^{3}\) and 500.0 singly charged negative ions per \(\mathrm{cm}^{3} ;\) ignore the presence of multiply charged ions. The electric field is $100.0 \mathrm{V} / \mathrm{m},$ directed downward. (a) In which direction do the positive ions move? The negative ions? (b) What is the direction of the current due to these ions? (c) The measured resistivity of the air in the region is $4.0 \times 10^{13} \Omega \cdot \mathrm{m} .$ Calculate the drift speed of the ions, assuming it to be the same for positive and negative ions. [Hint: Consider a vertical tube of air of length \(L\) and cross-sectional area \(A\) How is the potential difference across the tube related to the electric field strength?] (d) If these conditions existed over the entire surface of the Earth, what is the total current due to the movement of ions in the air?
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