If a beam of electromagnetic radiation has an intensity of 120 W/m2,
what is the maximum value of the electric field? (c = 3.0 x 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A) 1.5 kV/m
B) 1.0 µT
C) 1.0 µV/m
D) 0.30 kV/m
E) 0.0032 V/m
D
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To determine the thermal conductivity of a structural material, a large 15 cm-thick slab of the material was subjected to a uniform heat flux of 2500 W/m2 , while thermocouples embedded in the wall 2.5 cm. intervals are read over a period of time. After the system had reached equilibrium, an operator recorded the thermocouple readings shown below for two different environmental conditions
From these data, determine an approximate expression for the thermal conductivity as a
function of temperature between 40 and 208°C.
GIVEN
Thermal conductivity test on a large, 6-in.-thick slab
Thermocouples are embedded in the wall 2 in. apart
Heat flux (q/A) = 2500 W/m2
Two equilibrium conditions were recorded (shown above)
FIND
An approximate expression for thermal conductivity as a function of temperature between 40 and
2080C
ASSUMPTIONS
One dimensional conduction
SKETCH
Molecules in a region of expanding air more often collide with neighboring molecules that are
A) approaching. B) receding. C) nearly out of range.
Susan Solomon led the scientific expedition that
A) measured the rate of temperature increase at isolated places on earth, such as the north pole and the Gobi desert. B) studied the problem of ozone depletion over Antarctica. C) measured the carbon-dioxide content of the atmosphere at many places on Earth. D) measured the ozone content of the upper atmosphere at many places above the surface of the earth. E) studied in detail the atmospheric effects (especially carbon-dioxide injections) of large active volcanoes.
A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?
A) 0.28 kg ? m/s B) 0.88 kg ? m/s C) 0.44 kg ? m/s D) 0.62 kg ? m/s E) 1.4 kg ? m/s