A cup of coffee is enclosed on all sides in an insulated container 1/2 cm thick in the shape of a cube 10 cm on a side. The temperature of the coffee is 95°C, and the temperature of the surroundings is 21°C. Find the rate of heat loss (in J/s) due to conduction if the thermal conductivity of the cup is 2 × 10^?4 cal/s/cm/°C
a. 62
b. 74
c. 230
d. 160
e. 12
b
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Why do astronomers believe supermassive black holes are the source of an AGN's energy?
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LC Circuits: A series circuit contains an 80-?F capacitor, a 0.020-H inductor, and a switch. The resistance of the circuit is negligible. Initially, the switch is open, the capacitor voltage is 50 V, and the current in the inductor is zero. At time t = 0 s, the switch is closed. What is the maximum current in the circuit?
A. 2.2 A B. 2.4 A C. 2.8 A D. 3.0 A E. 3.2 A
To burn a hole in a piece of paper using light from the Sun, which mirror would work the best?
A) Plane B) Convex C) Concave D) All of the given answers would work equally as well. E) None of the given answers would burn a hole.
When a liquid boils and changes to a gas, it is said to have undergone a change of ________
Fill in the blank(s) with correct word