A brass cube, 13.0 cm on a side, is raised in temperature by 239°C. The coefficient of volume expansion of brass is 57 × 10^?6/C°. By what percentage is any one of the 13.0-cm edges increased in length?
a. 0.34%
b. 5.9%
c. 0.45%
d. 1.8%
e. 4.3%
c
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Which of the following is not suitable for studying biological material?
(a) An optical microscope (b) A high-voltage TEM (c) A STM (d) An AFM
Unpolarized light passes through three ideal polarizing filters. The first filter is oriented with a horizontal transmission axis, the second one has its transmission axis at 30° from the horizontal,
and the third filter has a vertical transmission axis. What percent of the light gets through this combination? A) 9.4% B) 91% C) 50% D) 0% E) 33%
A long solenoid (radius = 3.0 cm, 2 500 turns per meter) carries a current given by I = 0.30 sin(200 t) A, where t is measured in s. When t = 2.5 ms, what is the magnitude of the induced electric field at a point which is 4.0 cm from the axis of the solenoid?
a. 9.3 × 10^?3 V/m b. 8.0 × 10^?3 V/m c. 6.7 × 10^?3 V/m d. 5.3 × 10^?3 V/m e. 1.9 × 10^?3 V/m
A long, heated, cylindrical steel rod is removed from a heat treatment furnace and has to be cooled to complete the process. If the surface temperature of the rod is at 150°C and the cooling fluid temperature is maintained at 25°C, what is the minimum diameter of the rod to produce turbulent natural convection heat transfer if it is held in a horizontal position in (a) air and (b) water? Also, determine the initial heat transfer rate by natural convection from a 10-cm diameter rod in each of the two fluids.
GIVEN
• Long heated cylindrical steel rod, cooled by natural convection.
• Surface temperature of rod (Ts=1500C
• Fluid temperature (T?) = 250C
FIND
(a) Minimum diameter of rod to produce turbulent natural convection in (i) Air (ii) water
(b) Initial heat transfer rate by natural convection from 10 cm diameter rod in each fluids.
ASSUMPTIONS
• Radiation is negligible
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 87.5°C
Thermal expansion coefficient (?) = 0.00277 1/K
Thermal conductivity (k) = 0.0298 W/(m K)
Kinematic viscosity (?) = 22.55 × 10–6 m2/s
Prandtl number (Pr) = 0.71
for water at the mean temperature of 87.5°C
Thermal expansion coefficient (?) = 0.000678 1/K
Thermal conductivity (k) = 0.6765 W/(m K)
Kinematic viscosity (?) = 0.33 × 10–6 m2/s
Prandtl number (Pr) = 67.8