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Physics > Heat > Flashcards

Heat Flashcards

1
Q

What is heat?

A

Heat is a form of energy produced by the conversion of other forms of energy. It can also be defined as the total kinetic energy of the molecules of any substance.

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2
Q

List some forms of energy that can be converted into heat energy.

A
  • Mechanical Energy
  • Electrical Energy
  • Chemical Energy
  • Radiant Energy
  • Nuclear Energy
  • Sun
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3
Q

What happens when a gas is compressed?

A

The gas becomes warm or hot.

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4
Q

What is thermal efficiency?

A

The relationship between the potential power contained in a specific heat source and how much usable power is created when that heat source is used.

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5
Q

Fill in the blank: One BTU of heat energy equals ______ ft-lb of work.

A

778

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6
Q

How much heat energy does one pound of aviation gasoline contain?

A

18,900 BTU

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7
Q

What are the three methods of heat transfer?

A
  • Conduction
  • Convection
  • Radiation
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8
Q

True or False: Gases are better conductors of heat than solids.

A

False

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9
Q

What is conduction?

A

Heat transfer that occurs through physical contact between objects with differing heat energy.

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10
Q

What is convection?

A

The process by which heat is transferred by the movement of a heated fluid (gas or liquid).

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11
Q

Define radiation in the context of heat transfer.

A

The continual emission of energy from the surface of all bodies in the form of electromagnetic waves.

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12
Q

What is specific heat?

A

The quantity of heat required to change the temperature of a unit mass of a substance by 1 °C.

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13
Q

What are the three temperature scales used extensively?

A
  • Centigrade
  • Fahrenheit
  • Absolute (Kelvin)
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14
Q

Fill in the blank: The freezing point of water on the Fahrenheit scale is ______.

A

32°

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15
Q

What is thermal expansion?

A

The increase in volume of solids, liquids, and gases when they are heated.

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16
Q

What is the coefficient of linear expansion?

A

The amount that a unit length of any substance expands for a one degree rise in temperature.

17
Q

How does the specific heat of water affect climate?

A

Water’s high specific heat capacity helps maintain a constant temperature in the environment.

18
Q

What is the formula for calculating thermal efficiency?

A

Thermal Efficiency = Horsepower Produced ÷ Potential Horsepower in Fuel

19
Q

True or False: Radiation can travel through a vacuum.

A

True

20
Q

What are the effects of thermal efficiency losses in an engine?

A

More than 70 percent of the energy in the fuel is wasted, primarily as friction and heat.

21
Q

What is the primary reason solids expand less than liquids and gases?

A

The molecules of solids are much closer together and are more strongly attracted to each other.

22
Q

Which law is discussed in relation to the expansion of fluids?

A

Boyle’s law.

23
Q

What must be measured experimentally for thermal expansion in solids?

A

The exact rate of expansion or coefficient of expansion.

24
Q

What three pieces of information are necessary to estimate the expansion of an object?

A

Length, rise in temperature, and coefficient of expansion.

25
Q

What is the formula for calculating expansion?

A

Expansion = (coefficient) × (length) × (rise in temperature).

26
Q

If a steel rod measures 9 ft at 21 °C, what is its length at 55 °C with a coefficient of expansion of 11 × 10−6?

A

9.003366 ft.

27
Q

What is the increase in length of the steel rod when heated from 21 °C to 55 °C?

A

0.003366 feet or approximately 4/100 of an inch.

28
Q

What could happen if a steel rod could not expand freely when subjected to thermal expansion?

A

A tremendous force could be exerted due to thermal expansion.

29
Q

When designing which types of equipment must thermal expansion be considered?

A

Airframes, power plants, or related equipment.

Physics (12 decks)

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