4- The molecular weight of tungsten is 183.84 gr/mol, ts density is 19.25 gr/cm3, the resistivity of tungsten at 20 °C is 5.6x10-8 Qm and its a coefficient is 0.0045 °C-1. Since tungsten has 2 free electrons (ē) per current- carrying atom, a-) Find the drift velocity of electrons in a tungsten wire of 18 m length, 6 mm radius and 80 mA current at 20 °C. b-) Find the current density (1), conductivity (0), electric field in the wire (E) and resistance (R20). -) Find the resistance of this wire at 1080°C (R1080°c).

4- The molecular weight of tungsten is 183.84 gr/mol, ts density is 19.25 gr/cm3, the resistivity of tungsten at 20 °C is 5.6x10-8 Qm and its a coefficient is 0.0045 °C-1. Since tungsten has 2 free electrons (ē) per current- carrying atom, a-) Find the drift velocity of electrons in a tungsten wire of 18 m length, 6 mm radius and 80 mA current at 20 °C. b-) Find the current density (1), conductivity (0), electric field in the wire (E) and resistance (R20). -) Find the resistance of this wire at 1080°C (R1080°c).

Physics for Scientists and Engineers, Technology Update (No access codes included)

9th Edition

ISBN:9781305116399

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter27: Current And Resistance

Section: Chapter Questions

Problem 27.75AP: Review. When a straight wire is warmed, its resistance is given by R = R0,[1 + a(T T0)] according...

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Review. When a straight wire is warmed, its resistance is given by R = R0,[1 + a(T T0)] according to Equation 27.20, where a is the temperature coefficient of resistivity. This expression needs to be modified if we include the change in dimensions of the wire due to thermal expansion. For a copper wire of radius 0.100 0 mm and length 2.000 m, find its resistance at 100.0C, including the effects of both thermal expansion and temperature variation of resistivity. Assume the coefficients are known to four significant figures.
How does the resistance for copper and for silicon change with temperature? Why are the behaviors of these two materials different?
When a straight wire is heated, its resistance changes according to the equation R = R0 [1 + (T T0)] (Eq. 17.7), where is the temperature coefficient of resistivity. (a) Show that a more precise result, which includes the length and area of a wire change when it is heated, is R=R0[1+(TT0)][1+(TT0)][1+2(TT0)] where is the coefficient of linear expansion. (See Topic 10.) (b) Compare the two results for a 2.00-m-long copper wire of radius 0.100 mm, starting at 20.0C and heated to 100.0C.
Residential building codes typically require the use of 12-gauge copper wire (diameter 0.205 cm) for wiring receptacles. Such circuits carry currents as large as 20.0 A. If a wire of smaller diameter (with a higher gauge number) carried that much current, the wire could rise to a high temperature and cause a fire. (a) Calculate the rate at which internal energy is produced in 1.00 m of 12-gauge copper wire carrying 20.0 A. (b) Repeat the calculation for a 12-gauge aluminum wire. (c) Explain whether a 12-gauge aluminum wire would be as safe as a copper wire.
When a straight wire is heated, its resistance changes according to the equation R = R0 [1 + (T T0)] (Eq. 17.7), where is the temperature coefficient of resistivity. (a) Show that a more precise result, which includes the length and area of a wire change when it is heated, is R=R0[1+(TT0)][1+(TT0)][1+2(TT0)] where is the coefficient of linear expansion. (See Topic 10.) (b) Compare the two results for a 2.00-m-long copper wire of radius 0.100 mm, starting at 20.0C and heated to 100.0C.
Check Your Understanding Copper wires use routinely used for extension cords and house wiring for several reasons. Copper has the highest electrical conductivity rating, and therefore the lowest resistivity rating, of all nonprecious metals. Also important is the tensile strength, where the tensile strength is a measure of the force required to pull an object to the point where it breaks. The tensile strength of a material is the maximumamount of tensile stress it can take before breaking. Copper has a high tensile strength, 2108Nm2 A thirdimportant characteristic is ductility. Ductility is a measure of a material’s ability to be drawn into wires and a measure of the flexibility of the material, and copper has a high ductility. Summarizing, for a conductor to be a suitable candidate for making wire, there are at least three important characteristics: low resistivity, high tensile strength, and high ductility. What other materials are used for wiring and what are the advantages and disadvantages?
What current flows through a 2.54-cm-diameter rod of Pure silicon that is 20.0 cm long, when 1.00103 V is applied to it? (Such a rod may be used to make nuclear- particle detectors, for example.)
The diameter of wire A is greater than the diameter of wire B, but their lengths and resistivities are identical. For a given voltage difference across the ends, what is the relationship between PA and PB, the dissipated power for wires A and B, respectively? (a) PA = PB (b) PA PB (c) PA PB
Consider a power plant is located 60 km away from a residential area uses Q-gauge (A=42.40mm2) wire ofcopper to transmit power at a current of I = 100.00 A.How much more power is dissipated in the copper wires than it would be in superconducting wires?
-gauge copper wire has a diameter of 9.266 mm. Calculate the power loss in a kilometer of such wire when it carries 1.00102 A.
A coaxial cable consists of an inner conductor with radius r1=0.25cm and an outer radius of r0=0.5cm and has a length of 10 meters. Plastic, with a resistivityof =2.001013m m, separates the two conductors. What is the resistance of the cable?
4) Gold wire Al = 10 m long cylindrical wire made of gold (resis- tivity pAu = 2.44 × 10¬8 Nm at To = 20° C, temperature coefficient aAu = 3.4 x 10-3 (°C)¯) has a resistance of R = 12. a: What is the radius r of the wire? b: If the wire is twice as long, the radius is ... 1. twice as big O 2. 2 larger O 3. a fourth O c: What is the resistance of the wire at T 1000° C? %3D