A magnetic field exerts a force on an electric charge if the charge is
a. positive.
b. negative.
c. moving.
d. stationary.
e. any of the above.
c
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Compared with an alcohol barometer, the column height for a mercury barometer would be
A) lower. B) higher. C) the same.
The Earth's orbit is closest to the Sun in January and farthest from the Sun in July. When is the Earth moving the slowest in orbit?
a. Neither January nor July since the orbital speed of the Earth is a constant. b. January c. July d. This occurs twice a year, in April and in October.
A thin-wall jacketed tank, heated by condensing steam at one atmosphere contains 91 kg of agitated water. The heat transfer area of the jacket is 0.9 m2 and the overall heat transfer coefficient U = 227 W/(m2 K) based on that area. Determine the heating time required for an increase in temperature from 16°C to 60°C.
GIVEN
• A thin wall jacketed tank, heated by condensing steam
• Steam pressure = one atmosphere
• Mass of water in the tank = 91 kg
• The heat transfer area (A) = 0.9 m2
• The overall heat transfer coefficient (U) = 227 W/(m2 K) based on that area
• Temperature increases from 16°C to 60°C
FIND
• Determine the heating time required
ASSUMPTIONS
• Uniform water temperature due to agitation
• Thermal capacitance of the tank wall is negligible
SKETCH
Energy Levels: What is the wavelength of the photon emitted when an electron in a hydrogen atom which is in the initial state n = 8 jumps to the final state n = 2? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A. 205 nm B. 104 nm C. 389 nm D. 486 nm E. 610 nm