Heat+Transfer+Conduction+Convection+Radiation

Testing Conductivity of Different metals: Bend copper, aluminum and iron wire into identical L shapes. Solder the backs of the iron and aluminum wires together making a T. Now solder the back of the copper L to the others. (The base of the copper L can be bent up for storing flat.) Drip wax similar amounts of wax on the tips of each metal and let it harden. Now heat the solder backs of three wires with a candle. Watch to see the order in which the wax drips melt to see the relative conductivity of the metals.

Melting by convection vs. radiation of thermal energy. Define convection and radiation Drip wax on the end of a toothpick. Hold the drip under and close to the flame and watch it melt.

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The matter is present around us, in three states, solid, liquid and gas. The conversion of matter from one state to another is termed as a change in state, that takes place due to the exchange of heat between the matter and its surroundings. So, heat is the transition of energy from one system to another, due to the difference in temperature, which occurs in three different ways, that are conduction, convection and radiation.

 While **conduction ** is the transfer of heat energy by direct contact, **convection ** is the movement of heat by actual motion of matter; **radiation ** is the transfer of energy with the help of electromagnetic waves. People often misconstrue, these forms of heat transfer but, they are based on diverse physical interaction to transfer energy. To study the difference between conduction, convection and radiation, let’s take a look at the article provided below.

Conduction can be understood as the process, which enables direct transfer of heat through the matter, due to the difference in temperature, between adjacent parts of the object. It happens when the temperature of the molecules present in a substance increase, resulting in vigorous vibration. The molecules collide with surrounding molecules, making them vibrate too, resulting in the transportation of thermal energy to neighboring part of the object. In simple terms, whenever two objects are in direct contact with one another, there will be a transfer of heat from the hotter object to the colder one, which is due to conduction. Further, the objects which permit heat to travel easily through them are called conductors.
 * Definition of @Conduction **

Definition of Convection
In science, Convection implies the form of heat transfer, by real movement of matter, that occurs only in fluids. Fluid alludes to any substance, whose molecules move freely from one place to another, such as liquid and gases. It happens naturally or even forcefully. <span style="color: #222222; font-family: Arial,sans-serif; font-size: 14.66px;">Gravity has a great role to play in natural convection such that when the substance is heated from below, leads to the expansion of the hotter part. Due to buoyancy, the hotter substance rises as it is less dense and the colder substance replaces it by sinking at the bottom, due to high density, which when gets hot moves upward, and the process continues. In convection, on heating up the substance, it’s molecules disperse and moves apart. <span style="color: #222222; font-family: Arial,sans-serif; font-size: 14.66px;">When the convection is performed forcefully, the substance is compelled to move upwards by any physical means such as the pump. E.g. Air heating system.

<span style="color: #222222; font-family: Arial,sans-serif; font-size: 14.66px;">Definition of Radiation
<span style="color: #222222; font-family: Arial,sans-serif; font-size: 14.66px;">The heat transfer mechanism in which no medium is required is called radiation. It refers to the movement of heat in waves, as it does not need molecules to travel through. The object need not be in direct contact with one another to transmit heat. Whenever you feel heat without actually touching the object, it is because of radiation. Moreover, color, surface orientation, etc. are some of the surface properties on which radiation depends greatly. <span style="color: #222222; font-family: Arial,sans-serif; font-size: 14.66px;">In this process, the energy is transmitted through electromagnetic waves called as radiant energy. Hot objects generally emit thermal energy to cooler surroundings. Radiant energy is capable of travelling in the vacuum from its source to the cooler surroundings. The best example of radiation is solar energy that we get from the sun, even though, it is miles a way from us.

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<span style="background-color: transparent; color: #000000; display: block; font-family: arial,helvetica,sans-serif; font-size: 13px; text-align: left; text-decoration: none;">https://www.teachengineering.org/lessons/view/duk_heattransfer_smary_less

<span style="background-color: transparent; color: #000000; display: block; font-family: arial,helvetica,sans-serif; font-size: 13px; text-align: left; text-decoration: none;"><span style="background-color: #ffffff; color: #444444; font-family: arial,helvetica,sans-serif;">For these demonstrations, have ready a birthday candle poked into the bottom of an upside-down paper cup for each team, as well as the other materials mentioned in the demo descriptions below.

<span style="background-color: transparent; color: #000000; display: block; font-family: arial,helvetica,sans-serif; font-size: 13px; text-align: left; text-decoration: none;"><span style="background-color: #ffffff; color: #444444; font-family: arial,helvetica,sans-serif;">//Conduction Demo:// To experience conduction, have students put one end of a metal rod or spoon directly in the flame or just above it. The end of the metal soon heats up. The heat then spreads by conduction to the fingers of the person holding it. If you provide metal rods of various lengths, students could determine how long it takes the heat to travel out to their fingers for the different lengths. Short lengths of copper pipe (donated by a local plumber or plumbing supply store) are ideal, since copper has a very high conductivity.

<span style="background-color: transparent; color: #000000; display: block; font-family: arial,helvetica,sans-serif; font-size: 13px; text-align: left; text-decoration: none;"><span style="background-color: #ffffff; color: #444444; font-family: arial,helvetica,sans-serif;">//Convection Demo:// If students can sit very still without talking, they should be able to see smoke rising from the candle by free convection. This is easier to see if they briefly pinch the flame out, leaving the tip of the wick glowing—and smoking. They can also try holding an aluminum foil pie pan (obtained from grocery stores) upside down about an inch above the flame. After a few moments, the smoke accumulates under the pie plate and then begins to escape out around its edges, where it curls up toward the ceiling. Be sure to distinguish between the smoke and the heat, however. The smoke allows us to see the movement of the heated air, but it is not the heat itself. (A very smoky alternative to a birthday candle is a "bug coil," but this might set off a smoke detector alarm! If no breeze, the bug-coil demonstration is well suited for outdoors.)

<span style="background-color: transparent; color: #000000; display: block; font-family: arial,helvetica,sans-serif; font-size: 13px; text-align: left; text-decoration: none;"><span style="background-color: #ffffff; color: #444444; font-family: arial,helvetica,sans-serif;">//Radiation Demo:// To see the effects of radiation, have students coat the tip of a toothpick with a bit of wax as it melts and runs down the side of the candle. If they let the wax harden for a few moments, they can then move the toothpick slowly toward the flame. They must, however, approach the flame from below, and they should not let the wax tip touch the flame. Rather, when the tip gets a centimeter or two from the flame, they should see the wax begin to melt. Since the tip is not touching the flame, the wax cannot be melting due to conduction. Since the tip is below the flame, it cannot be melting due to convection. Instead, the wax melts because of the heat radiated from the flame.