The diameter of a 12-gauge copper wire is 0.081 in. The maximum ...

[Kikoku]

The diameter of a 12-gauge copper wire is 0.081 in. The maximum safe current it can carry (in order to prevent fire danger in building construction) is 20 A.
 
  At this current, what is the drift velocity of the electrons? The number of electron carriers in 1.0 cm3 of copper is 8.5  1022 and e = 1.60  10-19 C. A) 0.044 mm/s
  B) 0.44 mm/s
  C) 0.44 cm/s
  D) 0.44 m/s
  E) 4.4 cm/s

Question 2

At what temperature would the root-mean-square speed (thermal speed) of oxygen molecules be 13.0 m/s? Assume that oxygen approximates an ideal gas. The mass of one O2 molecule is 5.312 x 10-26 kg. The Boltzmann constant is 1.38  10-23 J/K.
 
  A) 0.217 K B) 0.0666 K C) 1800 K D) 5410 K

[underwood14]

Answer to Question 1

B

Answer to Question 2

A