Author Question: Building codes usually limit the current carried by a No. 14 copper wire to 15 A. Many household ... (Read 78 times)

imowrer · **on:** Jul 29, 2018

Building codes usually limit the current carried by a No. 14 copper wire to 15 A. Many household circuits are wired with this size wire. What is the drift velocity of the electrons in this case? The diameter of this wire is 1.6 mm.

Assume one conduction electron per atom in copper. The atomic weight of copper is 63.3 g/mol and its density is 8900 kg/m3. Avogadro's number is 6.022 1023 molecules/mol and e = 1.60 10-19 C.
A) 5.51 10-4 m/s
B) 1.65 10-3 m/s
C) 4.56 10-4 m/s
D) 4.89 10-5 m/s
E) 4.44 10-2 m/s

Question 2

A crystal diffracts a beam of electrons, like a grating, as they hit it perpendicular to its surface.

The crystal spacing is 0.18 nm, and the first maximum scattering occurs at 80 relative to the normal to the surface. (e = 1.60 10-19 C, melectron = 9.11 10-13 kg, h = 6.626 10-34 J s)
(a) What is the wavelength of the electrons?
(b) What potential difference accelerated the electrons if they started from rest?