Thermometers are used to measure the temperature of all sorts of things, from a fever to the heat in an oven to the weather. Various thermometers exist with various scales for temperature measurement. Take this quiz to see how much you know about thermometers.
A thermometer measures the effect of temperature on a material. Since materials expand and contract with temperature changes, you can measure the temperature based on how much the constant volume of material inside the thermometer, such as mercury, changes.
Temperature is measured in degrees.
On the Fahrenheit scale, the zero point represents the temperature of a mixture of ice and salt. This was the lowest temperature achievable when this scale was created in the early 1800s. The freezing point of water on this scale is 32 and the boiling point is 212.
Both the Rankine and Fahrenheit scales have a 180-degree difference between the freezing and boiling points of water and they are both primarily used in America, the Rankine usually by engineers. However, the zero point on the Rankine scale is absolute zero, which is -479.7 degrees on the Fahrenheit scale, a lot less than zero degrees Fahrenheit!
On the Celsius scale the difference between the freezing and boiling points of water is 100 degrees. This is why it is also called the centigrade scale, from the Latin word centi for hundred.
Physicists primarily use the Kelvin scale when they are working with very low temperatures.
The unit of the Kelvin scales is a kelvin, rather than a degree, although one kelvin is equal to one degree Celsius.
On both the Rankine and Kelvin scales, zero is absolute zero. This means you won't find negative numbers on these scales, since absolute zero is the lowest temperature theoretically possible.
The correct equation to convert Celsius to Fahrenheit is F = (9/5)C + 32. To convert Fahrenheit to Celsius, the equation is C = 5/9(F - 32)
A liquid-in-glass thermometer is the most commonly used.
Both mercury and alcohol can be used in a liquid-in-glass thermometer. Alcohol is usually dyed red so that it is visible.
The strip is usually spiral or in a rod shape. When affected by temperature the spiral winds or unwinds and the rod bends.
As its names suggests, the thermocouple uses a couple of different metals.
You would often find a bimetal thermometer in a thermostat.
The ear thermometer measures infrared radiation, a form of heat, in the ear drum.
Liquid-crystal thermometers are the ones you use on your forehead. Different mixtures of liquid crystals are used, each becoming lighter in color at a specific temperature. The colors correspond to a number on a temperature scale which is printed on the thermometer.
Pressure is measured by gas thermometers, since there is a known relationship between the pressure of gas confined to a constant volume and temperature, making it easy to calculate temperature if you know the pressure.
In 1731 French physicist Ren Antoine Raumur created the Raumur scale, which set the freezing point of water at zero degrees.
Galileo Galilei invented what he called the thermoscope in 1593.
The German physicist Gabriel Fahrenheit invented the mercury thermometer in 1714.