Power: A resistance heater is rated at 1200 W when operating at 110 V dc. What current will it draw?
A. 0.090 A
B. 1.0 A
C. 11 A
D. 12 A
Answer: C
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In chemistry, oxidation occurs when a substance
A) loses electrons B) rearranges its electrons internally C) accepts electrons D) breaks into its constituent atoms
When air contains as much water vapor as it can possibly hold for a given temperature, the air is at
A) capacity. B) optimum threshold. C) its evaporation point. D) sublimation point.
The ability of a telescope to separate two closely spaced stars is called ________
Fill in the blank(s) with correct word
A laboratory apparatus is used to maintain a horizontal slab of ice at -2.2°C so that specimens can be prepared on the surface of the ice and kept close to 0°C. If the ice is 10 cm by 3.8 cm and the laboratory is kept at 16°C, find the cooling rate in watts that the apparatus must provide to the ice.
GIVEN
• A slab of ice in a laboratory
• Ice temperature (Ti) = -2.2°C
• Ice dimensions: 10 cm by 3.8 cm
• Ambient temperature (T?) = 16°C
FIND
• The cooling rate (q) in watts
ASSUMPTIONS
• Air in the laboratory is still
• Effects of sublimation are negligible
• Effects of moisture in the air are negligible
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 6.9°C
Thermal expansion coefficient (?) = 0.0036 1/K
Thermal conductivity (k) = 0.0242 W/(m K)
Kinematic viscosity (?) = 14.51*10-6 m2/s
Prandtl number (Pr) = 0.71