The ________ spitting of the spectral lines is due to a strong magnetic field present
Fill in the blank(s) with correct word
Zeeman
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Seen from the northern latitudes (mid-northern hemisphere), the star Polaris
a. is never above the horizon during the day. b. always sets directly in the west. c. is always above the northern horizon. d. is never visible during the winter. e. is the brightest star in the sky.
What is true of Jupiter's magnetosphere?
A) Although its surface field is greater, since the planet is larger the total field is actually weaker than Earth's. B) It does not trap protons and electrons, as Earth's Van Allen belts do. C) It has a tail that extends at least to Saturn's orbit. D) It is most extensive on the sunward side of the planet. E) It is only slightly stronger than Saturn's.
Mercury is to be evaporated at 317°C in a furnace. The mercury flows through a 25.4 mm BWG No. 18 gauge 304 stainless-steel tube, that is placed in the center of the furnace. The furnace cross section, perpendicular to the tube axis, is a square 20 cm by 20 cm. The furnace is made of brick having an emissivity of 0.85, and its walls maintained uniformly at 977°C. If the convection heat transfer coefficient on the inside of the tube is 2.8 kW/(m2 K) and the emittance of the outer surface of the tube is 0.60, calculate the rate of heat transfer per meter of tube, neglecting convection within the furnace.
GIVEN
Mercury flow through a tube in the center of a furnace
Mercury temperature (Tm) = 317°C = 590 K
Tube specification: 25.4 mm BWG no 18 gauge stainless steel
Furnace cross section is 20 cm x 20 cm = 0.2 m x 0.2 m
Furnace emissivity (Tube specification: 25.4 mm BWG no 18 gauge stainless steel
Furnace wall temperature (T2) = 977°C = 1250 K
Tube interior heat transfer coefficient (hci) = 2800 W/(m2 K)
Tube exterior emissivity (?1) = 0.602) = 0.85
FIND
The rate of heat transfer per meter of tube
ASSUMPTIONS
Steady state
Convection within the furnace is negligible
SKETCH
the Stephan-Boltzmann constant
for 25.4 mm 18 BWG tubes
Inside diameter (Di) = 22.9 mm= 0.0229 m
Outside diameter (Do) = 25.4 mm = 0.0254 m
for type 304 stainless steel,the thermal conductivity (ks) = 14.4 W/(m K)
Two charged particles repel each other with a force F. If the charge of both particles is tripled and the distance between them is also tripled, then the force will be
A) F. B) 2 F. C) F/2. D) F/4. E) none of the above