Term
| Please mention the different way to assess temperature. |
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Definition
• the physiological sensation delivered through the receptor cells
• by comparison with a reference temperature
• by the work provided during a perfect thermodynamic process and a reference temperature
• via the entropy
• statistically via the average kinetic energy of molecules |
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Term
| Please indicate the relation between the above definitions of temperature and the laws of thermodynamics: |
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Definition
• only the physiological sensation
• zeroth law of thermodynamics
• Carnot cycle
• second law of thermodynamics
• statistically |
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Term
| Give the formula for linear expansion |
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Definition
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Term
| Which main factors that can lead to a deviation from linearity? |
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Definition
| the temperature dependence of α |
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Term
| Does the physical state of the material play a role? |
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Definition
| Yes, for liquid: vapor pressure, for gases: pressure and volume |
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Term
| Define the formula of linear Volume expansion? |
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Definition
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Term
| In a first approximation, what is the relation between the linear expansion and the Volume expansion? |
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Definition
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Term
| What requirements and simplifications are valid for this first approximation? |
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Definition
| The terms of higher order are neglected |
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Term
| What is the vapor pressure? |
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Definition
| Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. |
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Term
| How are vapour pressure and temperature related? |
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Definition
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Term
| Which thermometric liquid do you know? |
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Definition
• Water
• Ethanol
• Ethyl ether
• Ethyl chloride
• Propane
• Xylene |
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Term
| What are the principles of activation of an expansion thermometer? |
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Definition
| Volume expansion - i.e is the rate of change of that volume with temperature. This means that the volume of a material changes by some fixed fractional amount. |
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Term
| What are different types of expansion thermometer? |
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Definition
• Liquid glass thermometer
• Liquid spring thermometer
• Vapor pressure spring thermometer
• Rod expansion thermometer
• Bimetal thermometers |
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Term
| What is expansion actuating? |
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Definition
| The use of a strong dependency of volume-temperature for the production of a movement |
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Term
| What expansion actuators do you know? |
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Definition
• Bimetallic actuators
• Thermal mechanic micro relay |
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Term
| What is the working principle of shape memory alloys? |
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Definition
| Shape memory alloys can have two different crystal structures depending on the temperature and the external load which is austenite(heated and Straight and Martensite (cooled and zigzag) |
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Term
| What effects of shape memory alloys do you know? |
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Definition
• One-way effect
• [image]
Two-way effect |
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Term
| What is the Seebeck effect? (Verbal description) |
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Definition
| The temperature difference between two contact points of dissimilar metals or semiconductors cause a voltage drop in the open circuit |
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Term
| What is Thomson-Effect? (Verbal description) |
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Definition
| The temperature difference between two ends of a conductor causes a voltage drop between the ends |
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Term
| What is the Peltier effect? (Verbal description) |
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Definition
| Current flow in a circuit causes a temperature difference between two contact points of dissimilar metals or semiconductors |
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Term
| What is the defining equation of the Seebeck coefficient? What information should it include? |
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Definition
| a_AB= dU_AB/dT, the combination of materials |
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Term
| Please explain the Seebeck effect at a pn semiconductor junction using the band model: |
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Definition
|
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Term
| The thermal stress in the metal is in the order of: |
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Definition
|
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Term
| The thermal stress in the semiconductors is in the order of |
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Definition
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Term
| What is the general definition of the temperature coefficient (TCR) of electrical resistances? |
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Definition
|
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Term
| What factors determine the electrical resistance of metals: |
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Definition
• The mobility free charge carriers (μ in cm2 / V * s)
• The density of free charge carriers (n in cm-3) |
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Term
| What approximation can you make to estimate the temperature dependence of an electrical resistance using the above assumptions? |
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Definition
| The thermal expansion (change in geometry) should be neglected |
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Term
| How to specify the temperature dependence of electrical resistance in a simplified form: |
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Definition
| Through a series, specifying the coefficients and their signs |
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Term
| If one takes into account the non-linearity up to the third element, how would this look like? |
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Definition
| RT = R0 (1+A*T+B*T²+C*T³) |
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Term
| One specificity of the approximation of the Pt-characteristic curve is that is |
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Definition
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Term
| The metal resistors are characterized by the fact that their resistance increases with rising temperature. Therefore, they are called PTC. |
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Definition
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Term
| The metal resistors are characterized by the fact that their resistance increases with rising temperature. Therefore, they are called PTC. |
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Definition
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Term
| The linear temperature coefficient of metal resistance is in the order of 0.1% to 1% in the microstructure |
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Definition
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Term
| The value of the linear temperature coefficient for miscible metals can be adjusted by changing the amount of alloys components |
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Definition
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Term
| Miniaturized designs of metal resistors are produced by means of thin-film technology |
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Definition
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Term
| Substrates for miniaturized designs of metal resistors are usually glass or ceramics. |
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Definition
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Term
| Classic designs of metal resistors are mostly embedded in glass. |
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Definition
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Term
| Miniaturized designs of metal resistors are brought to their set points by a technique called trimming. To allow this, one has to embed trim structures in the design. |
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Definition
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Term
| The largest application areas for sensors based on metal resistances are: |
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Definition
Process technology
• Heating and air conditioning (heat meters, fireplace and boiler temperature sensors)
• Home appliances (hot plates)
• Automotive technology (current intake measurement, catalyst sensor)
• Refrigeration |
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Term
| The metal resistors display a low resistance; therefore to evaluate their value, it is recommended to use a four-point measurement technique with voltage comparison with a reference resistor. |
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Definition
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Term
| The conductivity of PTC thermistors increases with decreasing temperature. |
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Definition
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Term
| There are two groups of PTC sensors based on their basic material: |
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Definition
• Silicon (semiconductor)
• Ceramics |
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Term
| For the ceramic PTC thermistors, the grain boundary charges are compensated by the dipole field of the ferroelectric materials. |
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Definition
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Term
| Spreading resistance structures are operated at temperatures that are below the intrinsic activation energy. |
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Definition
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Term
| Spreading resistance are structures with a definite geometric arrangement of its contacts on the semiconducting substrates. |
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Definition
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