Chapter 26, Problem 9Q

An electric current of 5 A passing through a resistor has a measured voltage of 6 V across the resistor. The resistor is cylindrical with a diameter of 2.5 cm and length of 15 cm. The resistor has a uniform temperature of 90°C and the room air temperature is 20°C. Assuming that heat transfer by radiation is negligible, determine the heat transfer coefficient by convection.

A conducting cylinder has length 36 mm and radius 17 mm.  The conductor is then reshaped into a smaller cylinder, a quarter of the original length, and half that of the original diameter.  The conductivity of the material is 6x107/Ω.m.  Enter your answer in scientific notation with 2 significant figures. Please calculate the resistance for the reshaped conductor

A wire with a radius of 7.72mm is made of a conducting material that has an atomic mass of 49.4 grams/mole and a mass density of 7.78x10³ kg/m³. You can assume that each atom of the material has one free electron associated with it. What is the drift velocity in a 17.6 cm long section of wire that is carrying 704 Amps? Assume 3 significant digits and units of mm/s. Watch out for units!

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 2.221  at 20.0°C and increases to 4.307  as the indium starts to melt. αtungsten = 4.50 x 10−3 (°C)−1. What is the melting temperature of indium in °C?

按ESC | 即可退出全屏模式 Gas insulation is important for transmission lines, outdoor insulators and Gas-insulated- Substations (GIS). Understanding the breakdown mechanisms and behaviour of insulation materials is key to the optimum design of insulation systems. The speed distribution function of electrons in a gas containing electrons, ions and atoms is controlled by the electric field strength, E, and can be expressed as fo (E, v). It satisfies the relationship of (E, v) dv=1. i) ii) Convert the above electron speed distribution function into an electron energy distribution function that satisfies the relationship f(E, ɛ) dɛ =1 where & is the electron energy and ƒ(E, ɛ) the electron energy distribution function. The electron number density is ne and the atom number density is na in the gas. The ionisation cross section of the atoms by electron impact is a function of electron energy, ɛ, and can be written as σ¡ (ɛ). Similarly, the attachment collision cross section between an electron and an…

A CONDUCTING WIRE OF CROSS-SECTION 0.1 MM^2 CARRIES A CURRENT OF 5A PRODUCED BY AN ELECTRIC FIELD AT 100 V/M.THE CONDUCTIVITY OF THE MATERIAL Is

Earth’s lower atmosphere contains negative and positive ions that are produced by radioactive elements in the soil and cosmic rays from space. In a certain region, the atmospheric electric field strength is 120 V/m and the field is directed vertically down.This field causes singly charged positive ions, at a density of 620 cm3, to drift downward and singly charged negative ions, at a density of 550 cm3, to drift upward. The measured conductivity of the air in that region is 2.70 * 10-14 (ohmm)-1. Calculate (a) the magnitude of the current density and (b) the ion drift speed, assumed to be the same for positive and negative ions.

Problem 5: Copper wire has a resistivity p = 1.7 x 10-8 2 m when at 20°C and it has a temperature coefficient a = 3.9 x 10-3 K-1. A solid cylinder of copper of length L = 75 cm and diameter D = 1.5 mm has one end held at T1 = 14°C and the other end is held at T2 = 240°C. The temperature increases linearly between the two ends of the cylinder. L T2 dx Part (a) Consider a thin slice of the copper cylinder of thickness dx that is located a distance x from the left end of the cylinder. Write an equation for the temperature of this slice in terms of the variables x, L, T1, and T2. Expression : T = Select from the variables below to write your expression. Note that all variables may not be required. a, B, 0, d, g, h, j, k, L, m, P, t, T1, T2, x Part (b) Determine the total resistance in milliohms. Numeric : A numeric value is expected and not an expression. R =

9 Figure 26-22 gives the drift speed Va vaof conduction electrons in a copper wire versus position x along the wire. The wire consists of three sections that differ in radius. Rank the three A sections according to the following в |с | Figure 26-22 Question 9. quantities, greatest first: (a) radius, (b) number of conduction electrons per cubic meter, (c) magnitude of electric field, (d) conductivity.