TemperatureWhy would someone designing a pipeline include these strange loops? Pipelines carrying liquids often contain loops such as these to allow for expansion and contraction as the temperature changes. We will study thermal expansion in this chapter
Temperature and the ZerothLaw of ThermodynamicsWe often associate the concept of temperature with how hot or cold an object feels when we touch it. Thus, our senses provide us with a qualitative indication of temperature. However, our senses are unreliable and often mislead us.
The zeroth law of thermodynamics. (a) and (b) If the temperatures of A and B are measured to be the same by placing them in thermal contact with a thermometer (object C), no energy will be exchanged between them when they are placed in thermal contact with each other (c).Thermal equilibrium is a situation in which two objects would not exchange energy by heat or electromagnetic radiation if they were placed in thermal contact.
Zeroth law of thermodynamicsIf objects A and B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each otherWe can think of temperature as the property that determines whether an object is in thermal equilibrium with other objects. Two objects in thermal equilibrium with each other are at the same temperature. Conversely, if two objects have different temperatures, then they are not in thermal equilibrium with each other.
Quick QuizTwo objects, with different sizes, masses, and temperatures, are placed in thermal contact. Energy travels (a) from the larger object to the smaller object (b) from the object with more mass to the one with less (c) from the object at higher temperature to the object at lower temperature
Thermometers and the CelsiusTemperature ScaleAll thermometers are based on the principle that some physical property of a system changes as the systems temperature changes. Some physical properties that change with temperature are the volume of a liquid, the dimensions of a solid, the pressure of a gas at constant volume, the volume of a gas at constant pressure, the electric resistance of a conductor, and the color of an object.
As a result of thermal expansion, the level of the mercury in the thermometer rises as the mercury is heated by water in the test tube.0C, this temperature is called the ice point of water100C, which is the steam point of water
The Constant-Volume Gas ThermometerThe physical change exploited in this device is the variation of pressure of a fixed volume of gas with temperature.A constant-volume gas thermometer measures the pressure of the gas contained in the flask immersed in the bath. The volume of gas in the flask is kept constant by raising or lowering reservoir B to keep the mercury level in column A constant.
A typical graph of pressure versus temperature taken with a constant-volume gas thermometer. The two dots represent known reference temperatures (the ice and steam points of water).
Pressure versus temperature for experimental trials in which gases have different pressures in a constant-volume gas thermometer. Note that, for all three trials, the pressure extrapolates to zero at the temperature -273.15C.
The Absolute Temperature Scale
Absolute temperatures at which various physical processes occur. Note that the scale is logarithmic.
Skala termometerair mendidihes mencairKelvinCelciusFahrenheitReamur3732731000212328005 + 27359 + 324
Bila belum ada skala ?denganL0 = panjang kolom ketika 0oL100 = panjang kolom ketika 100oLt = panjang kolom pada temperatur tertentu
Liquid-in-glassSifat termometrik:Perubahan volume ( yaitu perubahan panjang dari merkuri atau etanol )Keuntungan:Mudah digunakan, murah dan mudah dibawa.Kerugian:Mudah pecah, daerah pengukuran terbatas, tidak dapat digunakan untuk mengukur obyek kecil.Daerah Pengukuran:Merkuri : 234 723 K , Etanol : 173 K 323 K
Constant-Volume gas ThermometerSifat TermometrikTekanan pada gas dengan volume konstan.KeuntunganSkala absolut, akurat, daerah pengukuran lebarKerugianBentuk besar, respon lambat, sulit untuk mengukur obyek kecil.Daerah Pengukuran Temperatur3 500 K
ResistansiSifat TermometrikPerubahan resitansi dari bahan konduktor (Pt, Ni, dll.)KeuntunganAkurat, daerah pengukuran lebar, dapat didisain berbagai macam model.KerugianHarga mahal.Daerah Pengukuran Temperatur15 900 K
ThermocoupleSifat TermometrikGGL yang timbul karena dua metal berbeda dikontakkan.KeuntunganSensitif, respon cepat, daerah pengukuran lebar.KerugianTegangan kecil sehingga membutuhkan penguatanDaerah Pengukuran Temperatur25 1400 K
ThermistorSifat TermometrikPerubahan resistansi dari bahan semikonduktor (Si).KeuntunganMudah diaplikasikan dengan komputer, murah.KerugianKurang akurat.Daerah Pengukuran Temperatur200 700 K
Optical PyrometerSifat TermometrikPerubahan sifat material karena kena radiasi panas.KeuntunganTidak bersentuhan dengan obyek, mudah digunakan.KerugianMemerlukan kalibrasi, kurang akurat, mahal.Daerah PengukuranDiatas 1250 K