Number of photons emitted each second by a 100 W light bulb?

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A 0.7 mm diameter superconducting wire is composed of half copper and half superconductor. At 3.2 T it is capable of carrying 2110 Amps. Assume 4.5 cm of that wire slides perpendicularly to the magnetic field due to the Lorentz forces. How far, in meters, did the wire slide to generate 0.002 J heat, assuming all the frictional energy was converted to heat in the section of wire?

Answer 1

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Chapter 10, Problem 4C

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Number of photons emitted each second by a 100 W light bulb?

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A 0.7 mm diameter superconducting wire is composed of half copper and half superconductor. At 3.2 T it is capable of carrying 2110 Amps. Assume 4.5 cm of that wire slides perpendicularly to the magnetic field due to the Lorentz forces. How far, in meters, did the wire slide to generate 0.002 J heat, assuming all the frictional energy was converted to heat in the section of wire?

Photons released by nuclear decays tend to be in the MeV range, and atomic nuclei are a few femtometers (10-15 m) across. If a single proton trapped in an inescapable rectangular box releases a 1.3 MeV photon when dropping from the n = 2 to the n = 1 state, how wide is the box, in femtometers? You should find that this quick and dirty estimate is remarkably close to the real size of a nucleus! The proton mass is about 1.7 x 10-27 kg. 1 MeV = 1.6 x 10-13 J. Planck's constant is approximately h = 6.6 x 10-34 J s.

(b) Calculate the half width in nanometers for Doppler broadening of the 4s S 4p transition for atomic nickel at 361.939 nm (3619.39 Å) at a temperature of 20,000 K in both wavelength and frequency units. (e) Calculate the speed that an iron atom undergoing the 4s S 4p transition at 385.9911 nm (3859.911 Å) would have if the resulting line appeared at the rest wavelength for the same transition in nickel. (f) Compute the fraction of a sample of iron atoms at 10,000 K that would have the velocity calculatedin (e). (g) Create a spreadsheet to calculate the Doppler half width DlD in nanometers for the nickel and iron lines cited in (b) and (e) from 3000–10,000 K. (h) Consult the paper by Gornushkin et al. (note 10) and list the four sources of pressure broadening that they describe. Explain in detail how two of these sources originate in sample atoms.