Resistance and Resistivity: The resistivity of gold is 2.44 × 10-8 ? ? m at a temperature of 20°C. A gold wire that is 0.50 mm in diameter and 44 cm long carries a current of 380 mA. How many electrons each second pass a given cross section of the wire at 20°C? (e = 1.60 × 10-19 C)
A. 2.4 × 1018
B. 2.4 × 1017
C. 1.2 × 1022
D. 2.8 × 1014
E. 6.3 × 1015
Answer: A
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Total Internal Reflection: A point source of light is positioned 20.0 m below the surface of a lake. What is the diameter of the largest circle on the surface of the water through which light can emerge into the air? The index of refraction of water is 1.33.
Fill in the blank(s) with the appropriate word(s).
The speed of sound in air is dependent upon the air temperature and other factors. The speed of sound increases from 334 m/s to 341 m/s between 8:00am and 11:00am. If a horn produces sound with wavelength 0.75 m at 8:00am, what would it produce at 11:00am?
A. 73 cm B. 77 cm C. Not enough info given to solve. D. 75 cm
Lobsters live on the bottom of the ocean, which means their density is
A) greater than the density of sea water. B) equal to the density of sea water. C) less than the density of sea water.
A swimmer swims 20 laps in a north-south facing pool in 7.00 minutes. Her first lap is toward the north. Her displacement and average velocity are
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