Temperature is the amount of heat or cold in the atmosphere as measured by a thermometer in Celsius (C), Fahrenheit (F), or Kelvin (K). A conventional thermometer is made of mercury, red spirit, or green spirit in a glass tube and works on the idea that when heated, the liquid expands more than the glass. In fact, the expansion of water is so small that it can be ignored at normal temperatures, but many thermometers include some form of expansion valve to increase the range of readings that can be obtained.
Radioactive materials decay over time, producing particles that are absorbed into human lungs. When this radioactive material decays, it produces energy in the form of gamma rays that can be detected by sensors called scintillators. These sensors are used in medical imaging such as X-rays and computed tomography scans (CT scans). A scintillator is an optical device that emits light when exposed to gamma radiation.
Thermocouples consist of two wires with different temperatures attached to each other. As long as the circuit is closed, the wires will always remain at the same temperature. When one wire gets hotter than the other, it will cause a voltage difference between the two terminals. This voltage can then be measured using a voltmeter.
Luminophores are substances that emit light when they are excited by electromagnetic radiation (such as visible light or X-rays). The luminophore used in traditional thermometers is calorimetric dye.
A thermometer is commonly used to measure temperature. It typically consists of a glass tube with a bulb in the lower section of the tube that holds mercury, colored alcohol, or a volatile liquid to measure the degree or intensity of heat. Modern thermometers may use other materials to indicate temperature, such as LEDs or a ceramic material that glows red when it gets hot.
Heating elements in appliances like stoves and ovens are also measured with a thermometer. The temperature is read directly off the scale attached to the element.
Heat intensity is another matter entirely. It depends on how much energy is being applied to a given surface area. Heat intensity can be calculated by multiplying the total wattage used to heat an object by its surface area. For example, if an electric blanket uses two watts of power per square foot, then its total wattage output is 40 watts. Its heat intensity is 40 watts over 4 square feet = 160 degrees F.
The heat intensity of an object will normally increase as more electricity is passed through it. This is because electrons become energized when they move from state to state within an electrical component--and these states need to be separated by something so they don't accumulate and cause further movement.
The temperature of the air is measured using thermometers. The most common thermometers are made of a glass rod with a very thin tube within. The tube holds a liquid that is fed by a reservoir, or "bulb," at the thermometer's base. The liquid is sometimes mercury and occasionally red-colored alcohol. As heat passes through the bulb, it changes the temperature of the liquid inside the tube. The fluid then flows into the capillary where it warms up again and thus gives off heat to the surrounding atmosphere.
The amount of heat required to change the temperature of one pound of water by 1 degree Fahrenheit is called its "latent heat." Water always seeks its own equilibrium temperature, which is 32 degrees for ordinary water. If you raise the temperature of a cup of water from 100 degrees to 105 degrees, it will evaporate, leaving space for more water vapor to enter. At some point it will reach the new equilibrium temperature of 100 degrees and stop changing state.
As air moves over a surface, it can pick up or lose heat. So the temperature of air several feet above the ground is usually lower than the same distance down in the shade. Sunlight heats objects directly, but it also heats the air around them because gases like oxygen and nitrogen expand when they become hot. This expansion pushes away from the source of heat and so creates wind.