## How is heat energy found?

What is Heat?

Consider a very hot mug of coffee on the countertop of your kitchen. For discussion purposes, we will say that the cup of coffee has a temperature of 80°C and that the surroundings (countertop, air in the kitchen, etc.) has a temperature of 26°C. What do you suppose will happen in this situation? I suspect that you know that the cup of coffee will gradually cool down over time. At 80°C, you wouldn't dare drink the coffee. Even the coffee mug will likely be too hot to touch. But over time, both the coffee mug and the coffee will cool down. Soon it will be at a drinkable temperature. And if you resist the temptation to drink the coffee, it will eventually reach room temperature. The coffee cools from 80°C to about 26°C. So what is happening over the course of time to cause the coffee to cool down? The answer to this question can be both macroscopic and particulate in nature.

This is largely a matter of semantics, but is probably worth trying to clarify. "Heat" refers to a TRANSFER of energy due to a difference of temperature. ("Work" is another way of energy transfer, caused by a force acting on an object as it moves over a distance interval. The FIRST LAW OF THERMODYNAMICS states that these are the only two ways of energy transfer. The three categories of heat are conduction, convection, and electromagnetic radiation.)

The energy that is transferred via heat is often called "thermal energy." The total energy content of a system (apart from kinetic energy due to overall motion of the entire system or potential energy due to the position of the entire system) is called its "internal energy." Under equilibrium conditions, this internal energy is shared equally (averaged over time) among the many ways the particles in the system have of possessing energy (kT/2 for each "degree of freedom" and in each particle, where k is the Boltzmann constant = 1.38x10^-23 Joules/K and T is the temperature in Kelvins.)

When heat is transferred, the hotter system loses internal energy, the cooler system gains it. On a microscopic level, this means that, on average, each particle's energy is reduced: its kinetic energy is reduced; for diatomic or polyatomic molecules, the energy in vibrations and rotations is reduced.

The semantics IS a little confusing and, in fact, the word "heat" is often used to mean thermal energy, or even internal energy. And sometimes the phrase "transfer of heat" is used - which is technically a redundancy, but . . . I recommend a good physics text.

The law is: no mass/energy may be created or destroyed. Ever.

Practically speaking, barring nuclear reactions, no energy can ever be cfreated or destroyed.

Now heat is a form of energy. It has some unusual thermodynamic properties, but it can no more be created or destroyed as any other. So when faced with your question, it becomes, "What forms of energy can be converted into heat?"

So:

Electrical energy can be converted into heat by forcing current through a resistor, as in range's heating coil.

Sound: sound energy, when absorbed, moves the molecules of the absorber and causes bind vibration, which is the physical manifestation of a heated substance.

EM waves (radio, infrared, visible light, UV, x-rays, gamma rays) - These, one and all, move molecules and orbital electrons and nuclei in atoms which absorb them. Once again, heat. Microwaves do likewise but are tuned to pick on water and fat molecular bonds, which is why they seem so effective.

Kinetic energy is converted to heat when friction occurs.

Potential energy is the same as kinetic energy, but it only happens when objects are squeezed by the gravity causing the potentiality.

Nuclear energy is pretty obvious where ever nuclear energy is used, as in a bomb or reactor.

Heat is a form of energy which is developed or transformation. But we neither create nor destroyed. For example if two bodies collide because of friction heat developed at contact point and transformed through out body.

Firstly we have to know that what is energy. energy is the power derived from any physical or chemical change. As we know that we produce heat by physical and chemical methods . Also we need to know that the ability or capacity to do something or act on a particular way is known as power.

The transfer or flow due to the difference in temperature between the two objects is called heat.

It is not easy to contain heat energy. Once produced say by staying in sun, or burning wood, or starting an electric heater, the heat energy is propagated in three different ways; conduction, convection and radiation. Thermos flasks are used to keep hot objects like coffee hot (or cold objects cold) for some more time. The vacuum present in the two concentric glass containers of the thermos flask reduces conduction losses, the wooden cork reduces the convection losses and silvered glass walls reduce the radiation losses. Nothing is perfect. Heat eventually radiates away increasing the entropy/chaos in the Universe. And the coffee gets cold.

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