Temperature Flashcards
state the law of conservation of energy
energy is never created or destroyed, only transferred from one form to another
define thermal energy
Thermal energy is the energy transferred from a region of higher temperature to a region of lower temperature
what does temp tell us
direction of energy flow when 2 regions are in contact- hotter to cooler
define thermal equilibrium
When two substances in physical contact with each other no longer exchange any heat energy and both reach an equal temperature
what is A thermometer
A thermometer is any device that is used to measure temperature
what property does a liquid in glass thermometer depend on
density of liquid. it expands with temp increase and moves along capillary tube
what property does a gas thermometer depend on
Volume of gas at constant pressure. As the temperature of the gas increases, its volume increases and vice versa (how quick volume increases with temp)
what property does a thermistor based thermometer depend on
resistance.
it decreases with temp increase. changes rapidly over narrow range of temps.
Non linear so curve so must be calibrated
what is a thermocouple
an electrical device used as the sensor of a thermometer
It consists of two wires of different metals attached to each other, producing a junction on one end. The opposite ends are connected to a voltmeter. When this junction is heated, an e.m.f. is produced between the two wires which is measured on the voltmeter. The greater the difference in temperature between the wires, the greater the e.m.f
thermocouple graph
non linear so needs calibration
purpose of the Kelvin/thermodynamic scale
overcome issue with sclaes of temp
said to be an absolute scale that is not defined in terms of a property of any particular substance
This is because thermodynamic temperaturesdo not dependon the property of any particular substance
define absolute zero on the kelvin scale
The lowest temperature possible. Equal to 0 K or -273.15 °C
define absolute zero in kinetic terms
The temperature at which the atoms and molecules in all substances have zero kinetic and potential energy (so internal energy is also zero)
so impossible to remove energy from sth at 0K
relationship between C and K temp
A change in a temperature of 1 K is equal to a change in temperature of 1oC
how to go from K to C
-273.15
technical word for thermistors and thermocouples
temp sensors
advantages of thermistor
It is veryrobustie. strong and doesn’t easily break
Highly sensitiveover a narrow range of temperatures
disadvantages of thermistor
Only anarrow rangeof temperatures can be read
Difficult to get accurate readings
Non-linear readings
advantages of thermocouple
It isrobust
Can detect awide rangeoftemperatures (Veryaccuratereadings)
Low thermal capacity, therefore, quicker acting
Small so can measure at any point
Long conducting wires allow the operator to be at a distance from the thermocouple
disadvantages of thermocouple
variation means calibration is required
give 2 observations which woud support the idea that temperature doesnt measure amount of thermal energy/heat in a body
- when heat is added to melt/boil temp doesnt change
- 2 objects of diff mass and same material would need diff amounts of heat to reacht at temp (iebig tub a lot energy but small temp and vice versa)
when temp is not changing its either cos of change in state or …
rate heat lost= heat input
whats sensitivity
large change in a property for small change
