The diameter of no. 12 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 one cubic centimeter of copper is 8.5 1022.)
Question 2A 3 kg mass is positioned at (0, 8), and a 1 kg mass is positioned at (12, 0). What are the coordinates of a 4 kg mass which will result in the center of mass of the system of three masses being located at the origin (0, 0)?
A) (-3, -6)
B) (-6, -3)
C) (3, 6)
D) (-12, -8)
Question 3When a light wave enters into a medium of different optical density
A) its speed and frequency change.
B) its speed and wavelength change.
C) its frequency and wavelength change.
D) its speed, frequency, and wavelength change.
Question 4One cat meowing produces a sound intensity level of 55. db.
(a) What would be the sound intensity level of 2 cats meowing?
(b) ... of 10 cats meowing?
(c) ... of 100 cats meowing?
Question 5Most of the carbon dioxide on the Earth
A) is dissolved in the oceans, forming carbonate rocks
B) has frozen out in the polar regions
C) has escaped into space
D) is still present in the atmosphere
Question 6What is the change of entropy associated with 3.0 kg of water freezing to ice at 0.C?
A) -1.1 kcal/K
B) -0.88 kcal/K
C) 0 kcal/K
D) 1.0 kcal/K
E) +0.88 kcal/K
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