<< Chapter < Page Chapter >> Page >

This law was postulated in the 1930s, after the first and second laws of thermodynamics had been developed and named. It is called the zeroth law because it comes logically before the first and second laws (discussed in Thermodynamics ). An example of this law in action is seen in babies in incubators: babies in incubators normally have very few clothes on, so to an observer they look as if they may not be warm enough. However, the temperature of the air, the cot, and the baby is the same, because they are in thermal equilibrium, which is accomplished by maintaining air temperature to keep the baby comfortable.

Does the temperature of a body depend on its size?

No, the system can be divided into smaller parts each of which is at the same temperature. We say that the temperature is an intensive quantity. Intensive quantities are independent of size.

Got questions? Get instant answers now!

Section summary

  • Temperature is the quantity measured by a thermometer.
  • Temperature is related to the average kinetic energy of atoms and molecules in a system.
  • Absolute zero is the temperature at which there is no molecular motion.
  • There are three main temperature scales: Celsius, Fahrenheit, and Kelvin.
  • Temperatures on one scale can be converted to temperatures on another scale using the following equations:
    T º F = 9 5 T º C + 32 size 12{T rSub { size 8{°F} } = { {9} over {5} } T rSub { size 8{°C} } +"32"} {}
    T º C = 5 9 T º F 32 size 12{T rSub { size 8{°C} } = { {5} over {9} } left (T rSub { size 8{°F} } - "32" right )} {}
    T K = T º C + 273 . 15 size 12{T rSub { size 8{K} } =T rSub { size 8{°C} } +"273" "." "15"} {}
    T º C = T K 273 . 15 size 12{T rSub { size 8{°C} } =T rSub { size 8{K} } - "273" "." "15"} {}
  • Systems are in thermal equilibrium when they have the same temperature.
  • Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy.
  • The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.

Conceptual questions

What does it mean to say that two systems are in thermal equilibrium?

Got questions? Get instant answers now!

Give an example of a physical property that varies with temperature and describe how it is used to measure temperature.

Got questions? Get instant answers now!

When a cold alcohol thermometer is placed in a hot liquid, the column of alcohol goes down slightly before going up. Explain why.

Got questions? Get instant answers now!

If you add boiling water to a cup at room temperature, what would you expect the final equilibrium temperature of the unit to be? You will need to include the surroundings as part of the system. Consider the zeroth law of thermodynamics.

Got questions? Get instant answers now!

Problems&Exercises

What is the Fahrenheit temperature of a person with a 39 . 0 º C size 12{"39" "." 0°C} {} fever?

102 º F size 12{"102"°F} {}

Got questions? Get instant answers now!

Frost damage to most plants occurs at temperatures of 28 . 0 º F size 12{"28" "." 0°F} {} or lower. What is this temperature on the Kelvin scale?

Got questions? Get instant answers now!

To conserve energy, room temperatures are kept at 68 . 0 º F size 12{"68" "." 0°F} {} in the winter and 78 . 0 º F size 12{"78" "." 0°F} {} in the summer. What are these temperatures on the Celsius scale?

20 . 0 º C size 12{"20" "." 0°C} {} and 25 . 6 º C size 12{"25" "." 6°C} {}

Got questions? Get instant answers now!

A tungsten light bulb filament may operate at 2900 K. What is its Fahrenheit temperature? What is this on the Celsius scale?

Got questions? Get instant answers now!

The surface temperature of the Sun is about 5750 K. What is this temperature on the Fahrenheit scale?

9890 º F size 12{"9890"°F} {}

Got questions? Get instant answers now!

One of the hottest temperatures ever recorded on the surface of Earth was 134 º F size 12{"134"°F} {} in Death Valley, CA. What is this temperature in Celsius degrees? What is this temperature in Kelvin?

Got questions? Get instant answers now!

(a) Suppose a cold front blows into your locale and drops the temperature by 40.0 Fahrenheit degrees. How many degrees Celsius does the temperature decrease when there is a 40 . 0 º F size 12{"40" "." 0°F} {} decrease in temperature? (b) Show that any change in temperature in Fahrenheit degrees is nine-fifths the change in Celsius degrees.

(a) 22 . 2 º C size 12{"22" "." 2°C} {}

(b) Δ T º F = T 2 º F T 1 º F = 9 5 T 2 º C + 32 . 0 º 9 5 T 1 º C + 32 . 0 º = 9 5 T 2 º C T 1 º C = 9 5 Δ T º C

Got questions? Get instant answers now!

(a) At what temperature do the Fahrenheit and Celsius scales have the same numerical value? (b) At what temperature do the Fahrenheit and Kelvin scales have the same numerical value?

Got questions? Get instant answers now!

Questions & Answers

Is there a formula for time of free fall given that the body has initial velocity? In other words, formula for time that takes a downward-shot projectile to hit the ground. Thanks!
Cyclone Reply
hi
Agboro
hiii
Chandan
Hi
Sahim
hi
Jeff
hey
Priscilla
sup guys
Bile
Hy
Kulsum
What is unit of watt?
Kulsum
watt is the unit of power
Rahul
p=f.v
Rahul
watt can also be expressed as Nm/s
Rahul
2 forces whose resultant is 100N, are at right angle to each other .if one of them makes an angle of 30 degree with the resultant determine it's magnitude
Victor Reply
50 N... (50 *1.732)N
Sahim
Plz cheak the ans and give reply..
Sahim
Is earth is an inertial frame?
Sahim Reply
The abacus (plural abaci or abacuses), also called a counting frame, is a calculating tool that was in use in Europe, China and Russia, centuries before the adoption of the written Hindu–Arabic numeral system
Sahim
thanks
Irungu
Most welcome
Sahim
Hey.. I've a question.
Sahim Reply
Is earth inertia frame?
Sahim
only the center
Shii
What is an abucus?
Irungu
what would be the correct interrogation "what is time?" or "how much has your watch ticked?"
prakash Reply
a load of 20N on a wire of cross sectional area 8×10^-7m produces an extension of 10.4m. calculate the young modules of the material of the wire is of length 5m
Ebenezer Reply
Young's modulus = stress/strain strain = extension/length (x/l) stress = force/area (F/A) stress/strain is F l/A x
El
so solve it
Ebenezer
please
Ebenezer
two bodies x and y start from rest and move with uniform acceleration of a and 4a respectively. if the bodies cover the same distance in terms of tx and ty what is the ratio of tx to ty
Oluwatola Reply
what is cesium atoms?
prakash Reply
The atoms which form the element Cesium are known as Cesium atoms.
Naman
A material that combines with and removes trace gases from vacuum tubes.
Shankar
what is difference between entropy and heat capacity
Varun
Heat capacity can be defined as the amount of thermal energy required to warm the sample by 1°C. entropy is the disorder of the system. heat capacity is high when the disorder is high.
Chathu
I want learn physics
Vinodhini Reply
sir how to understanding clearly
Vinodhini
try to imagine everything you study in 3d
revolutionary
pls give me one title
Vinodhini
displacement acceleration how understand
Vinodhini
vernier caliper usage practically
Vinodhini
karthik sir is there
Vinodhini
what are the solution to all the exercise..?
What is realm
Vinodhini Reply
The quantum realm, also called the quantum scale, is a term of art inphysics referring to scales where quantum mechanical effects become important when studied as an isolated system. Typically, this means distances of 100 nanometers (10−9meters) or less or at very low temperature.
revolutionary
How to understand physics
Vinodhini Reply
i like physics very much
Vinodhini
i want know physics practically where used in daily life
Vinodhini
I want to teach physics very interesting to studentd
Vinodhini
how can you build interest in physics
Prince
by reading it
Austin
understanding difficult
Vinodhini
vinodhini mam, physics is used in our day to day life in all events..... everything happening around us can be explained in the base of physics..... saying simple stories happening in our daily life and relating it to physics and questioning students about how or why its happening like that can make
revolutionary
your class more interesting
revolutionary
anything send about physics daily life
Vinodhini
How to understand easily
Vinodhini
check out "LMES" youtube channel
revolutionary
even when you see this message in your phone...it works accord to a physics principle. you touch screen works based on physics, your internet works based on physics, etc....... check out google and search for it
revolutionary
what is mean by Newtonian principle of Relativity? definition and explanation with example
revolutionary Reply
what is art physics
Akinbulejo Reply
I've been trying to download a good and comprehensive textbook for physics, pls can somebody help me out?
Olanrewaju
try COLLEGE PHYSICS!! I think it will give you an edge.
Lawal
c=1/c1+c2/1+c3 what is the answer
Akinbulejo Reply
got on answers bro
smith
This may seem like a really stupid question, but is mechanical energy the same as potential energy? If not, what is the difference?
Nikki Reply
what is c=1\c1,c=2\c2,c=3\c3
Akinbulejo
mechanical energy is of two types 1: kinetic energy 2: potential energy,so, potential energy is actually the type of mechanical energy ,the mechanical due to position is designated as potential energy
Iram
Thank you!!!!!
Nikki
Can someone possibly walk me through this problem? " A worker drives a 0.500 kg spike into a rail tie with a 2.50 kg sledgehammer. The hammer hits the spike with a speed of 65.0 m/s. If one-third Of the hammer's kinetic energy is converted to the internal energy of rhe hammer and spike.
Nikki
how much does the total internal energy increase
Nikki
you know the mass and the velocity of the hammer. therefore using the equation (mv^2)/2 you can find the kinetic energy. then take one third of this value and that will be your change in internal energy. here, the important thing is that spike is stationary so it does not contribute to initial Energ
Chathu
Thabk you! :)
Nikki
Practice Key Terms 9

Get the best College physics course in your pocket!





Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics' conversation and receive update notifications?

Ask