An inductor has 200 turns/cm and a cross-sectional area of 1.8 cm2. If its inductance is 32 mH, what is its length?
A. 21 cm
B. 15 cm
C. 35 cm
D. 64 cm
E. 72 cm
C. 35 cm
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Consider the electrical space heater, where the electric resistance heating coil is enclosed in a straight horizontal polished metallic cylinder that has an outer diameter of 1 cm and an emissivity of 0.9. If its surface temperature is at 110°C and the room air temperature is at 20°C, calculate the total heat loss per unit length of the cylinder due to both convection and radiation. For the purpose of this calculation, assume that the reflector is so designed that it “collects” all of the radiant heat from the back half of the horizontal heater and that it reflects 95% of the incident radiation.
GIVEN
• An electric resistance heating coil enclosed in horizontal metallic cylinder.
• Emissivity (?) = 0.9
• Diameter of cylinder (D) = 1 cm= 0.01 m
• Surface temperature (Ts) = 110°C= 383 K
• Ambient air temperature (T?) = 20°C= 293 K
• Reflects 95% of incident radiation.
FIND
Total heat loss per unit length of cylinder due to convection and radiation.
ASSUMPTIONS
• Air is still
• Surface temperature is uniform and constant
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 65°C
Thermal expansion coefficient (?) = 0.00296 1/K
Thermal conductivity (k) = 0.02825 W/(m K)
Kinematic viscosity (?) = 19.92 × 10–6 m2/s
Prandtl number (Pr) = 0.71
Special relativity states the relationship between energy and mass as
a. True b. False Indicate whether the statement is true or false
Newton's Cradle consists of an aligned row of identical elastic balls suspended by strings so they barely touch one another. When two balls are raised from one end and released, they strike the row and two balls pop out from the other end
If instead, one ball popped out with twice the speed of the two, this would violate A) momentum conservation. B) energy conservation. C) both of these D) none of these
A particle whose mass is 2 kg moves in the xy plane with a constant speed of 3 m/s along the direction 
. What is its angular momentum (in kg?m2/s) relative to the origin?
A.
B.
C.
D.
E.