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Questions and Answers
What is the physical interpretation of heat?
What is the physical interpretation of heat?
- The movement of molecules and atoms within a substance.
- The work done by a system.
- The transfer of thermal energy. (correct)
- The temperature of a substance.
Two objects are in thermal equilibrium. According to the zeroth law of thermodynamics, what condition must be met?
Two objects are in thermal equilibrium. According to the zeroth law of thermodynamics, what condition must be met?
- The objects must have different temperatures.
- The net heat exchange between the objects must be zero. (correct)
- The objects must have the same mass.
- The objects must exchange heat until their temperatures are equal.
At what temperature do Celsius and Fahrenheit scales have the same numerical value?
At what temperature do Celsius and Fahrenheit scales have the same numerical value?
- 32°
- 100°
- -40° (correct)
- 0°
A metal rod is heated. Which of the following best describes the change in its length, assuming $\alpha$ is the coefficient of linear expansion and $\Delta T$ is the change in temperature?
A metal rod is heated. Which of the following best describes the change in its length, assuming $\alpha$ is the coefficient of linear expansion and $\Delta T$ is the change in temperature?
In the context of thermal expansion, what does the coefficient $\alpha$ represent?
In the context of thermal expansion, what does the coefficient $\alpha$ represent?
A bridge is constructed with segments of concrete. Why is thermal expansion an important consideration in its design?
A bridge is constructed with segments of concrete. Why is thermal expansion an important consideration in its design?
If the coefficient of linear expansion for steel is $12 \times 10^{-6} / \text{°C}$, what is the change in length of a 1-meter steel bar if its temperature increases by 45°C?
If the coefficient of linear expansion for steel is $12 \times 10^{-6} / \text{°C}$, what is the change in length of a 1-meter steel bar if its temperature increases by 45°C?
How is Kelvin defined?
How is Kelvin defined?
Which of the following is an example of thermal energy transfer?
Which of the following is an example of thermal energy transfer?
If a material has a high coefficient of thermal expansion, how will its volume change with an increase in temperature, compared to a material with a low coefficient of thermal expansion?
If a material has a high coefficient of thermal expansion, how will its volume change with an increase in temperature, compared to a material with a low coefficient of thermal expansion?
Flashcards
Heat
Heat
Transfer of thermal energy.
Temperature
Temperature
Movement of molecules/atoms of a given substance.
Zeroth Law of Thermodynamics
Zeroth Law of Thermodynamics
Objects are in equilibrium when heat exchange equals 0.
Celsius scale
Celsius scale
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Kelvin scale
Kelvin scale
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Expansion coefficient
Expansion coefficient
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Thermal expansion
Thermal expansion
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Thermal Expansion consideration
Thermal Expansion consideration
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Study Notes
Heat and Thermodynamics
- Heat (Q) is the transfer of thermal energy.
- Temperature (T) measures the movement of molecules/atoms in a substance (°F, °C, K).
- Two objects are in equilibrium when heat exchange equals zero (0th Law of Thermodynamics).
- Water freezes at 0°C, 32°F, 273K.
- Water boils at 100°C, 212°F, 373K.
- Celsius is defined by water.
- Kelvin is defined by absolute zero.
- Temperature in Fahrenheit can be determined by the formula TF = (5/9)TC + 32.
- Temperature in Kelvin can be determined by the formula TK = TC + 273.
- Celsius and Fahrenheit are equal at -40°.
Thermal Expansion
- Equation for linear thermal expansion: L = Lo(1 + αΔT), where L is the final length, Lo is the initial length, α is the expansion coefficient, and ΔT is the change in temperature.
- α, the expansion coefficient is around 10^-6
Golden Gate Bridge Example
- Initial length (Lo) = 1275m
- Initial temperature (To) = -15°C, final temperature = 40°C
- Expansion coefficient (α) = 12 * 10^-6
- The change in length (ΔL) for the Golden Gate Bridge is 0.84m
- ΔT(°C) = ΔT(K)
Volume Expansion
- Volume expansion equation: ΔV = l^3 * 3αΔT
- Use thermal expansion instead of volume expansion.
- Example using concrete with ΔT = 45°C and α = 12 x 10^-6 °C
- Spacing is .324 cm
- 1m of concrete expands for .54mm for a 45 degree change in temperature
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