A resistor has a resistance of 30 
at 20
C If the temperature coefficient is 
what is its resistance at 200
C?
A. 24 
B. 27
C. 48
D. 54
E. 57
D. 54
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The heating surface is gray (emissivity = 0.8) while the receiver has a black surface. The lower plate is heated uniformly over its surface with a power input of 300 W. Assuming that heat losses from the backs of the radiating surface and the receiver are negligible and that the surroundings are at a temperature of 27°C, calculate the following
A 10 cm square, electrically heated plate is placed in a horizontal position 5 cm below a second plate of the same size as shown schematically.
(a) The temperature of the receiver
(b) The temperature of the heated plate.
(c) The net radiation heat transfer between the two surfaces.
(d) The net radiation loss to the surroundings.
(e) Estimate the effect of natural convection between the two surfaces on the rate of
heat transfer.
GIVEN
A square heated plate below a second plate of equal size as shown above
Plate size = 10 cm x 10 cm = 0.1 m x 0.1 m
Distance between plates (L) = 5cm = 0.05 m
Heated surface (A1) is gray with an emissivity (?1) = 0.8
Receiver (A2) is black (?2 = 1.0)
Heater power input
FIND
(a) The temperature of the receiver (T2)
(b) The temperature of the heated transfer (T1)
(c) The net radiation heat transfer (q12)
(d) The net radiation loss to the surroundings (qs)
(e) Estimate the effect of natural convection
ASSUMPTIONS
Steady state
Heat losses from the back of each plate are negligible
Temperature of surroundings (T3) = 27°C = 300 K
The surroundings behave as a blackbody enclosure
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant
In Ptolemy's geocentric model, the planet's motion along its deferent is all that is needed to understand retrograde motion
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What will be an ideal response?
A principal mechanism for energy loss during nuclear fusion is bremsstrahlung. This loss is associated with
a. x-rays emitted due to electron-ion collisions. b. radiation losses due to T4 losses. c. conduction losses associated with ?T. d. convection losses associated with ?T. e. neutron collisions with atoms of moderator.