Answers to illustrative activity: Take a hot plate and turn it on. How is heat moving around it? Think about it, investigate it, talk to someone else about it.

Notice that it is hotter above the hot plate than it is on either side or below it. This is because of convection. The hot air, being less dense than the surrounding air, rises, carrying heat with it.

Since the air is rising, it either leaves a big hole in the air (not the right answer) or other air must move in to take its place (the right answer). You can use a piece of tissue paper to see the effects of the air moving in toward the hot plate. This is advection.

If you hold your hand to the side of the hot plate, or slightly below it, you can still feel the heat, even though advection and convection are carrying heat away from these locations. The heat arrives at these places by radiation. The glowing hot plate is radiating energy as visible light and infrared radiation.

If you touch the metal parts of the hotplate that are not being directly heated, you will notice they are warm (or really hot! Watch out!). These areas can heat up by conduction, because they are in contact with the hot part of the hot plate.

Also, how did the air near the hot plate get hot in the first place? It got hot primarily because it is in contact with the hotplate (conduction), and because the air may absorb some of the energy radiating from the hot plate (radiation).

Home Page (est.htm)     Previous Page (est1a.html)