Which of the following does not affect the conductivity of a material. a.) The resistivity of the material b.) The mean time per collision c.) The electron concentration of the material d.) None of the

Which of the following does not affect the conductivity of a material. a.) The resistivity of the material b.) The mean time per collision c.) The electron concentration of the material d.) None of the

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter28: Current And Resistance

Section: Chapter Questions

Problem 9PQ

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A close analogy exists between the flow of energy by heat because of a temperature difference (see Section 19.6) and the flow of electric charge because of a potential difference. In a metal, energy dQ and electrical charge dq are both transported by free electrons. Consequently, a good electrical conductor is usually a good thermal conductor as well. Consider a thin conducting slab of thickness dx, area A, and electrical conductivity , with a potential difference dV between opposite faces. (a) Show that the current I = dq/dt is given by the equation on the left: ChargeconductionThermalconductiondqdt=A|dVdx|dQdt=kA|dTdx| In the analogous thermal conduction equation on the right (Eq. 19.17), the rate dQ/dt of energy flow by heat (in SI units of joules per second) is due to a temperature gradient dT/dx in a material of thermal conductivity k. (b) State analogous rules relating the direction of the electric current to the change in potential and relating the direction of energy flow to the change in temperature.
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The following directly affects the conductivity of a material except one. Which is it? the electron concentration of the material; the mean time per collision; (The answer cannot be found on the other choices.) the resistivity of the material;
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Which of these are TRUE: 1. Benjamin Franklin interpreted the negative terminal as an area where it lacks electrons 2. Resistivity is measured in ohms. 3. At high temperature, the vibrations of the atoms of the conductor increases 4. A conductor has electric current with or without potential difference 5. Only electron flow is acceptable in interpreting current flow
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Q1 /A piece of metal is its length 5m and its cross-sectional area 0.5 mm^2 and the specific resistance of the metal is 81.6*10^6 Q– m Note that the density of The substance is 8.96 kg/m^3 and the atomic weight 63.54 calculate: 1) Calculate the motion of the electron (H). 2) Calculate the mean free time (7). 3) If you know that the density of electrons along the x-coordinate increases according to the relationship n = 1030 + 8 * 1033x + 15 * 1036 x2 The temperature is 290k, so what is the value of the diffusion current Id at the metal surface x=0 3) If the value of the propagation current is Id at the distance x From the surface of the metal are 91.2*10^10 A/m2 What is the value of x
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At the same temperature, two wires made of pure copper have different resistances. The same voltage is applied at the ends of each wire. The wires may differ in ( check all that apply) _ a. length _b. cross-sectional area _c. resistivity _d. amount of electric current passing through them Hint 1) The resistivity of a metallic conductor, such as copper, nearly always increases with increasing temperature. Hint 2) For an ohmic conductor, that is, a conductor such as copper that obeys Ohm's law, the resistance R is proportional to the length L and inversely proportional to the cross-sectional area A. That is, R=ρL/A where ρ ie. rho, is the resistivity of the material. Note that ρ is a characteristic of the specific material and may vary with temperature. Hint 3) Ohm's law tells us that the potential difference V between the ends of a conductor is equal to the product of the current I through the conductor and the conductor's resistance R, V=IR