A tantalum rod of diameter 3 mm and length 120 mm is supported by two electrodes within a large vacuum enclosure. Initially the rod is in equilibrium with the electrodes and its surroundings, which arc maintained at 300 K. Suddenly, an electrical current, I = 80 A , is passed through the rod. Assume the emissivity of the rod is 0. 1 and the electrical resistivity is 95 × 10 − 8 Ω ⋅ m . Use Table A.1 to obtain the other thermophysical properties required in your solution. Use a finite-difference method with a space increment of 10 mm. (a) Estimate the time required for the midlength of the rod to reach 1000K. (b) Determine the steady-state temperature distribution and estimate approximately how long it will take to reach this condition.
A tantalum rod of diameter 3 mm and length 120 mm is supported by two electrodes within a large vacuum enclosure. Initially the rod is in equilibrium with the electrodes and its surroundings, which arc maintained at 300 K. Suddenly, an electrical current, I = 80 A , is passed through the rod. Assume the emissivity of the rod is 0. 1 and the electrical resistivity is 95 × 10 − 8 Ω ⋅ m . Use Table A.1 to obtain the other thermophysical properties required in your solution. Use a finite-difference method with a space increment of 10 mm. (a) Estimate the time required for the midlength of the rod to reach 1000K. (b) Determine the steady-state temperature distribution and estimate approximately how long it will take to reach this condition.
Solution Summary: The author explains the minimum input power which affects the soldering. The thermal conductivity coefficient of copper is k=379W/m.
A tantalum rod of diameter 3 mm and length 120 mm is supported by two electrodes within a large vacuum enclosure. Initially the rod is in equilibrium with the electrodes and its surroundings, which arc maintained at 300 K. Suddenly, an electrical current,
I
=
80
A
, is passed through the rod. Assume the emissivity of the rod is 0. 1 and the electrical resistivity is
95
×
10
−
8
Ω
⋅
m
. Use Table A.1 to obtain the other thermophysical properties required in your solution. Use a finite-difference method with a space increment of 10 mm.
(a) Estimate the time required for the midlength of the rod to reach 1000K.
(b) Determine the steady-state temperature distribution and estimate approximately how long it will take to reach this condition.
Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies, v1 > v2, of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.
A thin tungsten filament with a length of 1.47 m radiates 60.2 W of power in the form of electromagnetic waves. A perfectly absorbing surface, in the form of a hollow cylinder with a radius of 5.09 cm and a length of 1.47, is placed concentrically with the filament. Calculate the radiation pressure acting on the cylinder. (Assume that the radiation is emitted in the radial direction, and neglect end effects.)
An atom in a state with l = 1 emits a photon with wavelength 600.000 nm as it decays to a state with l = 0. If the atom is placed in a magnetic field with magnitude B = 2.00 T, what are the shifts in the energy levels and in the wavelength that result from the interaction between the atom’s orbital magnetic moment and the magnetic field?
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