The figure shows a cross section of three parallel wires each carrying a current of 5.0 A out of the paper. If the distance R = 6.0 mm, what is the magnitude of the magnetic force on a 2.0-m length of any one of the wires?
a.
2.5 mN
b.
3.3 mN
c.
2.2 mN
d.
2.9 mN
e.
1.7 mN
d
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To decrease the size of personal computer mother boards, designers have turned to a more compact method of mounting memory chips on the board. The single in-line memory modules, as they are called, essentially mount the chips on their edges so that their thin dimension is horizontal, as shown in the sketch below. For safe operation (so that the VLSI microchips do not “burn out”), their maximum temperature always has to be <=75°C under all operating conditions. Assuming that the memory board, housing the chip modules, is also at the same temperature, determine the maximum power that is dissipated from the chips if the board is cooled by air at 20°C. The air flows perpendicular to the board face, as shown in the figure, with a velocity of 10 m/s. Consider the heat loss from both the
front face and back face of the memory-modules board. Is it beneficial (dissipate more heat) if the board was aligned parallel to the air flow? To model the board, in both cases, consider an equivalent “square” of the same rectangular face area and determine the appropriate length scale.
GIVEN
• Computer memory chip in an air stream as shown above
• Chip temperature (Ts) = 90°C
• Air temperature (T?) = 20°C
• Air velocity (U?) = 10 m/s FIND
• The maximum power dissipation ( Q G)
ASSUMPTIONS
• Radiative heat transfer is negligible
• Use for a non-square surface will not introduce significant error
• Heat transfer from all four edges of the chip is negligible
An incompressible fluid is flowing through a vertical pipe with a constriction. The wide section is 2.00 cm in diameter and is at the top of the pipe. The pressure of the fluid in the wide section at the top is 200 kPa. The velocity of the fluid in the wide section is 4.00 m/s. The narrow section is located 4.00 m below the wide section. What is the diameter of the narrow section for the pressure of the fluid in the narrow section to equal the pressure in the wide section? (density of the fluid is 680 
A. 1.50 cm B. 1.43 cm C. 1.36 cm D. 1.28 cm E. 1.15 cm
The element carbon, so important to life, was formed in the earliest nebulae of the Universe and thus became a component of all protostars.
a. true b. false
A champion athlete can produce one horsepower (746 W) for a short period of time. The number of 16 cm high steps a 70 kg athlete could ascend in one minute while expending one horsepower is
a. 4. b. 7. c. 65. d. 408. e. 4 567.