Heat transfer-Objective questions and answers

KAS Physics
Thermal Physics Test number 202

1. Radiation is the chief method of energy transfer
*a. from the sun to an earth satellite b. from a gas flame to water in a teakettle
c. from a soldering iron to metals being soldered. d. from water to an ice cube floating in it e. from a mammal to the surrounding air.

2. of the processes below, the one in which practically all the heat transfer is by conduction is: a. from the sun to an earth satellite b. from a gas flame to the top layer of water in a teakettle. *c. from a soldering iron to metals being soldered d. from the bottom of a glass of water to an ice cube floating in it. e. from a mammal to the surrounding air.

3. two kg of water are heated by stirring, if this raises the temperature of the water from 15˚C to 25˚C, how much work, in joules, was done to the water by the stirring?
a. 20,000 b. 40,000 c. 60,000 *d. 80,000 e. 100,000

4. In a certain steam engine, the average pressure on the piston during a stroke is 50 N/m2. The length of each stroke is 12 cm, the area of the piston is 120 cm2 and the diameter of the flywheel is 5m. the amount of work done on the piston during each stroke is, in N-m, approximatelyy
a. 250 *b.0.072 c. 0.54 d.1.63 e. 12.62

5. the work done by a system is characterized as
*a. Positive b. Negative c. either positive or negative d. indeterminate
e. of no consequence

6. which of the following can actually lower the internal energy (cool) a room?
a. Fan b. refrigerator with door open
c. refrigerator with door closed d. an air conditioner in the middle of the room
*e. an air conditional partially exposed to the outside

7. 30 joules of heat flow into a system. the system in turn does 50 J of work. The internal energy of the system has
a. increased by 80 J b. decreased by 80 J c. increased by 20 J d. decreased by 20 J
*e. remained constant

8. dark, rough objects are generally good for
a. Conduction *b. Radiation c. Convection d. Reflection e. refraction

9. dark plastic handles are often used on kitchen utensils because
a. the black material is a good radiator *b. the plastic is a good insulator
c. The plasticic is a good conductor d. the plastic softens gradually with excessive heat.
e. the material is thermoplastic