PHY 101 exam 4

If you double the absolute temperature of a star, its power output increases by a factor of

16

If you double the radiating surface area of a star, its power output increases by a factor of

2

You are watching a science fiction movie where people on a spaceship are traveling around the universe observing stars with different temperatures. Which of the following stars has the lowest surface temperature?

A reddish star

Which of the following quantities is not conserved?

Entropy

Which Law of Thermodynamics relates change in internal energy to heat added to a system and work done by it?

First

In addition to heat energy, another product of fires is dangerous smoke and other chemicals. This fact is the reason for a ________ in a furnace.

Heat Exchanger

Why does the handle of a metal spoon submerged in boiling soup feel hot?

Heat from the soup is transferred through the spoon by conduction.

Why does an ice cube feel cold?

Heat from your hand enters the cube by conduction.

A Diesel engine is more efficient that a gasoline engine because

It has a higher temperature and can therefore convert more heat into work.

A shiny, white transparent surface prevents heat transfer because

It has emissivity of zero and reflects all light that strikes it.

The surface of the moon is exposed to full solar radiation because it has no atmosphere. Why then does the moon not heat up endlessly until it disintegrates?

Its temperature rises until it is able to radiate heat away into space as fast as it arrives from the sun.

Which temperature scale has 373 as the boiling point of water?

Kelvin

Who invented the internal combustion engine?

Otto

"The entropy of an isolated system never decreases." Which Law of Thermodynamics is this?

Second

What causes knocking in your car's engine?

The fuel ignites before it should.

You fill two identical mugs with coffee, but the coffee in one mug is at a higher temperature than that in the other mug. You place the two mugs simultaneously in a microwave oven and turn it on briefly. As a result, you add 1 joule of thermal energy to each mug. Which mug experiences the larger increase in entropy (if any)?

The mug containing the colder coffee experiences the larger increase in entropy.

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun rises near the seashore.

The surface wind will blow from the water toward the land.

How can you reduce knocking in your car's engine?

Use higher-octane gasoline

"Two objects in thermal equilibrium with a third object are in thermal equilibrium with each other." Which Law of Thermodynamics is this?

Zeroth

The first law of thermodynamics is a re-statement of the law of

conservation of energy

Wind is one of nature's ways of transferring energy through

convection.

Ice is

crystalline

In a car engine, the compression stroke involves the piston compressing the air/gas mixture so rapidly that virtually no heat loss can occur. In the compression stroke, the air/gas mixture

heats because work is being done on the air/gas mixture.

It is a hot summer day and your friend's apartment has no air conditioning. However, a brand new refrigerator lies unopened in the center of the living room. Being a creative person, your friend closes all the doors and windows of the apartment, unpacks the refrigerator, plugs it in, and turns it on. Your friend then opens the refrigerator door and uses a small fan to circulate the air past the refrigerator and throughout the room. After the refrigerator has operated for a few minutes, the average temperature in the room is

higher than it was before.

The "strokes", or "cycles" in a four-stroke engine are

induction, compression, power, exhaust

You are a mechanic in a garage and are working on a carburetor that is made of metal, has a glass inspection window and plastic gears for the choke. If all three types of material are at the same temperature and each type of material is in contact with the other two, then

no heat will flow between any parts.

Which temperature scale has 273 as the boiling point of water?

no scale

A pedestrian bridge crosses a street. This bridge is entirely supported by columns from below. A gap at each end of the bridge separates the bridge's surface from the sidewalks leading to the bridge. The width of each gap changes with time. This width is smallest

on hot days.

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because

radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation.

Moments before it is ignited by the spark plug, the mixture of fuel and air inside an automobile cylinder is compressed to very high density. During the compression process, the mixture's

temperature rises dramatically, and so does its pressure.

Some scientists assert that there would be no life on earth if ice did not have a molecular structure with a lot of open space because

the density of ice would be greater than water and lakes would freeze solid - from the bottom up.

When cooking a potato in a conventional oven (not a microwave) it is useful to stick a nail in it, which makes it cook faster. This is because

the nail is a good conductor of heat.

A popular classroom demonstration involves placing a paper cup with water in it on a burner and boiling the water in the cup. Although part of the cup may burn, the part containing the water does not because

the water absorbs most of the heat from the flame.

You open the refrigerator in your room and put in a case of room-temperature root beer. After an hour, the root beer is ice cold. If your room air did not exchange any heat with the outdoor air during that time, the room air will be

warmer because the refrigerator will have pumped heat out of the root beer and into the room air.

A common glass thermometer contains a red or silver liquid that rises upward in a glass tube as the temperature of the thermometer increases. The liquid moves up the tube because

while both the glass and the liquid expand as their temperatures increase, the liquid expands more rapidly than the glass does.