A circular loop (area = 0.20 m2) turns in a uniform magnetic field with B = 0.13 T. At an instant when the angle between the magnetic field and the normal to the plane of the loop is (?) rads and is decreasing at the rate of 0.50 rad/s, what is the magnitude of the emf induced in the loop?
a. zero
b. 13 mV
c. 26 mV
d. 20 mV
e. 18 mV
a
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About how many potentially hazardous asteroids pass within 0.05 AU of the Earth per decade in modern times?
A) None B) 10-20 C) 200-300 D) 5000-1000 E) A completely unknown quantity; it could easily be anywhere from just a few to millions.
Solar One, located near Barstow, CA, was the first large-scale (10 MW electric) solar- thermal electric-power-generating plant in the United States. A schematic diagram of the plant is shown below. The receiver may be treated as a cylinder 7 m in diameter and 13.5-m-tall. At the design operating conditions, the average outer surface temperature of the receiver is about 675°C and ambient air temperature is about 40°C. Estimate the rate of heat loss, in MW, from the receiver—via natural convection only—for the temperatures given. What are other mechanisms by which heat may be lost from the receiver?
GIVEN
• A vertical cylinder in air
• Height of cylinder (L) = 13.5 m
• Diameter (D) = 7 m
• Surface temperature (Ts) = 675°C
• Ambient air temperature (T?) = 40°C
FIND
(a) The rate of convective heat loss (qc) in MW
(b) What other mechanisms for heat loss exist?
ASSUMPTIONS
• Air is still
• Surface temperature is uniform and constant
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 357.5°C
Thermal expansion coefficient (?) = 0.00160 1/K
Thermal conductivity (k) = 0.0461 W/(m K)
Kinematic viscosity (?) = 58.1 × 10–6 m2/s
Prandtl number (Pr) = 0.72
How can a steam turbine use the heat of vaporization to increase the output of electrical energy it is generating?
: In an effort to increase the miles per gallon in automobiles many steel parts are being replaced with polymer parts where the strength of steel is not required.
The blades of the fan that cool the radiator experience a centripetal stress of less than 1×105 Pa when the fan blade material density is reduced to approximately 1×103 kg/m3. Vibration of the fan blades is the greatest problem, and vibration amplitude is minimized by maximizing the elastic modulus (stiffness) of the blade material. In addition it is determined that the Izod impact strength must be a minimum of 100 for sufficient resistance to fracture and fatigue. To control cost it is necessary to select a commodity polymer. Polymers with glass or other material reinforcement are too expensive for this design. What material discussed in this chapter would best suit the design requirements?