<< Chapter < Page Chapter >> Page >

Key equations

Linear thermal expansion Δ L = α L Δ T
Thermal expansion in two dimensions Δ A = 2 α A Δ T
Thermal expansion in three dimensions Δ V = β V Δ T
Heat transfer Q = m c Δ T
Transfer of heat in a calorimeter Q cold + Q hot = 0
Heat due to phase change (melting and freezing) Q = m L f
Heat due to phase change (evaporation and condensation) Q = m L v
Rate of conductive heat transfer P = k A ( T h T c ) d
Net rate of heat transfer by radiation P net = σ e A ( T 2 4 T 1 4 )

Conceptual questions

What are the main methods of heat transfer from the hot core of Earth to its surface? From Earth’s surface to outer space?

Got questions? Get instant answers now!

When our bodies get too warm, they respond by sweating and increasing blood circulation to the surface to transfer thermal energy away from the core. What effect will those processes have on a person in a 40.0 - ° C hot tub?

Increasing circulation to the surface will warm the person, as the temperature of the water is warmer than human body temperature. Sweating will cause no evaporative cooling under water or in the humid air immediately above the tub.

Got questions? Get instant answers now!

Shown below is a cut-away drawing of a thermos bottle (also known as a Dewar flask), which is a device designed specifically to slow down all forms of heat transfer. Explain the functions of the various parts, such as the vacuum, the silvering of the walls, the thin-walled long glass neck, the rubber support, the air layer, and the stopper.

Figure shows the cross section of a thermos. Glass walls with silvered surfaces form the inner container. It is suspended within the outer container with springs and rubber supports. There is a layer of air and a layer of vacuum between the two containers. the inner container is filled with hot or cold liquid.
Got questions? Get instant answers now!

Some electric stoves have a flat ceramic surface with heating elements hidden beneath. A pot placed over a heating element will be heated, while the surface only a few centimeters away is safe to touch. Why is ceramic, with a conductivity less than that of a metal but greater than that of a good insulator, an ideal choice for the stove top?

It spread the heat over the area above the heating elements, evening the temperature there, but does not spread the heat much beyond the heating elements.

Got questions? Get instant answers now!

Loose-fitting white clothing covering most of the body, shown below, is ideal for desert dwellers, both in the hot Sun and during cold evenings. Explain how such clothing is advantageous during both day and night.

Photograph of men wearing loose white clothing.
Got questions? Get instant answers now!

One way to make a fireplace more energy-efficient is to have room air circulate around the outside of the fire box and back into the room. Detail the methods of heat transfer involved.

Heat is conducted from the fire through the fire box to the circulating air and then convected by the air into the room (forced convection).

Got questions? Get instant answers now!

On cold, clear nights horses will sleep under the cover of large trees. How does this help them keep warm?

Got questions? Get instant answers now!

When watching a circus during the day in a large, dark-colored tent, you sense significant heat transfer from the tent. Explain why this occurs.

The tent is heated by the Sun and transfers heat to you by all three processes, especially radiation.

Got questions? Get instant answers now!

Satellites designed to observe the radiation from cold (3 K) dark space have sensors that are shaded from the Sun, Earth, and the Moon and are cooled to very low temperatures. Why must the sensors be at low temperature?

Got questions? Get instant answers now!

Why are thermometers that are used in weather stations shielded from the sunshine? What does a thermometer measure if it is shielded from the sunshine? What does it measure if it is not?

If shielded, it measures the air temperature. If not, it measures the combined effect of air temperature and net radiative heat gain from the Sun.

Got questions? Get instant answers now!

Questions & Answers

A proton initially at rest falls through a p.d of 25000V. what speed does it gain?
Minister Reply
what is the reaction of heat on magnet
ORIZINO Reply
what is a physical significant of electric dipole moment .
PRANAB Reply
A dipole moment it's a mechanical electrical effect used in nature
Antonio
what is the uses of carbon brushes in generator
Malik Reply
at what temperature is the degree Fahrenheit equal to degree Celsius
Grace Reply
Celsius and Faharaneith are different, never equal
Antonio
find their liners express of n=a+b/T² ( plot graph n against T)
Donsmart Reply
Radio Stations often advertis "instant news,,if that meens you can hear the news the instant the radio announcer speaks it is the claim true? what approximate time interval is required for a message to travel from Cairo to Aswan by radio waves (500km) (Assume the waves Casbe detected at this range )
mahmod Reply
what is growth and decay
Pawan Reply
thevenin
Oladejo Reply
Can someone please predict the trajectory of a point charge in a uniform electric field????
erlinda Reply
what is deference between strong force and coulomb force
zahid Reply
so basically the electric lines or the field lines
zach Reply
it's the measure of the flow of an electric field through a certain area
zach Reply
What is electric flux
Pranju Reply
how to calculate the magnetic force if the B field is depend on the coordinate
Ivan Reply
Practice Key Terms 9

Get the best University physics vol... course in your pocket!





Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'University physics volume 2' conversation and receive update notifications?

Ask