A filament of tungsten wire is 0.001 m in diameter, and the filament is heated to 2500 K. The work function of tungsten is 4.5 eV.
(a) Calculate the probability of electrons having sufficient energy to be emitted from the filament.
(b) Calculate the emission current density from the tungsten wire.
(c) What length of wire can produce a thermionic electron current of 1 A?
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Two speakers are placed side by side and driven by the same frequency of 0.50 kHz. If the distance from a person to one speaker is 5.0 m and the person detects little or no sound,
which of the following is a possible the distance from the person to the other speaker? The sound speed in the room is 340 m/s. A) 7.7 m B) 8.1 m C) 8.4 m D) 9.1 m
A 2.00-m long piano wire with a mass per unit length of 12.0 g/m is under a tension of 8.00 kN. What is the frequency of the fundamental mode of vibration of this wire?
A) 204 Hz B) 102 Hz C) 408 Hz D) 510 Hz E) 153 Hz
When you look at a white light through a blue piece of glass, you observe blue light. This means that the blue glass
A. absorbs all of the blue light. B. reflects all of the blue light. C. transmits all colors except blue. D. transmits only the blue light. E. transmits only cyan and magenta.
Which of the following is true of Mercury?
A) It has polar caps of solid water. B) It is 95 percent the size of Earth. C) It has negligible atmosphere. D) It is the fourth largest planet of the Solar System.