М. Өтемісов атындағы Батыс Қазақстан мемлекеттік университеті
Факультет: физика-математика
Кафедра: физика және Физика
Шифр, мамандық: 5В011000 – Физика
Пән: Кәсіби бағытталған шетел тілі
Билет №1
Read and retell the text:
Absolute humidity
Absolute humidity is the total mass of water vapor present in a given volume of air. It does not take temperature into consideration. Absolute humidity in the atmosphere ranges from near zero to roughly 30 grams per cubic meter when the air is saturated at 30 °C.
Absolute humidity is the mass of the water vapor
(
),
divided by the volume of the air and water vapor mixture (
),
which can be expressed as:
The absolute humidity changes as air temperature or pressure changes. This makes it unsuitable for chemical engineering calculations, e.g. for clothes dryers, where temperature can vary considerably. As a result, absolute humidity in chemical engineering may refer to mass of water vapor per unit mass of dry air, also known as the mass mixing ratio, which is better suited for heat and mass balance calculations. Mass of water per unit volume as in the equation above is also defined as volumetric humidity. Because of the potential confusion, British Standard BS 1339 (revised 2002) suggests avoiding the term "absolute humidity". Units should always be carefully checked. Many humidity charts are given in g/kg or kg/kg, but any mass units may be used.
The field concerned with the study of physical and thermodynamic properties of gas–vapor mixtures is named psychrometrics.
Explain the following formula:
Write definitions of the following terms: temperature, absolute humidity, chemical engineering, psychrometrics, volumetric humidity, mass mixing ratio.
Физика және математика кафедрасының отырысында қаралып, бекітілген.
Хаттама № «7 » __18_____ ____03______ 2015 ж.
Кафедра меңгерушісі:____________ Кульжумиева А.А.
Факультеттің ОӘК отырысында қаралып, бекітілген.
Хаттама № «7 » __19____ ____03_____ 2015 ж.
Факультеттің ОӘК төрағасы: _________ Иксебаева Ж.С.
М. Өтемісов атындағы Батыс Қазақстан мемлекеттік университеті
Факультет: физика-математика
Кафедра: физика және Физика
Шифр, мамандық: 5В011000 – Физика
Пән: Кәсіби бағытталған шетел тілі
Билет №2
Read and retell the text:
Absolute zero
Absolute zero is the lower limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as 0. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15° on the Celsius scale (International System of Units), which equates to −459.67° on the Fahrenheit scale (United States customary units). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition.
It is commonly thought of as the lowest temperature possible, but it is not the lowest enthalpy state possible, because all real substances begin to depart from the ideal gas when cooled as they approach the change of state to liquid, and then to solid; and the sum of the enthalpy of vaporization (gas to liquid) and enthalpy of fusion (liquid to solid) exceeds the ideal gas's change in enthalpy to absolute zero. In the quantum-mechanical description, matter (solid) at absolute zero is in its ground state, the point of lowest internal energy.
The laws of thermodynamics dictate that absolute zero cannot be reached using only thermodynamic means, as the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically. A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state at absolute zero. The kinetic energy of the ground state cannot be removed.
Scientists have achieved temperatures extremely close to absolute zero, where matter exhibits quantum effects such as superconductivity and superfluidity.