Why are temperature/voltage/etc not measured all in KJ?

  • Thread starter hexhunter
  • Start date
In summary, the different units for measuring energy are a legacy of earlier systems of measurement, and they are convenient to use.
  • #1
hexhunter
100
0
why are temperature/voltage/etc not measured all in KJ?

ditto...
 
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  • #2
Why?They're all other physical quantities.

Daniel.
 
  • #3
dextercioby said:
Why?They're all other physical quantities.

Daniel.

Yah what he said :P

Joules is a unit of work/heat. Temperature is a state variable. Voltage is another state variable. Its like asking why isn't mass measured in Joules.
 
  • #4
It's not necessarily thermodynamics.Voltage for example is not defined in thermodynamics.

Daniel.
 
  • #5
Voltage is already measured in joules/columb - energy / unit charge.

Temperature scales were around long before thermodynamics, so they are a bit of a legacy unit. And they are conveniently sized for everyday use.
 
  • #6
i mean, why aren't the energies measured in the same unit? also, chemical energy is measured in jouldes, in food atleast...

and i din't realize that joules were used for electricity

PS: I am only doing a single physics for my science GCSE, but next year i should hopefully be doing AS physics
 
Last edited:
  • #7
Energies are measured in various units.It's either erg,or Joule,or Calorie and many more.Between them there are the so-called CONVERSION RULES.Just like in the scales for temperature...

Daniel.
 
  • #8
We are unfortunate for having so many systems of measurement. This is not the case only with energy. Consider length, or mass. We have metres, miles, feet, inches, kg, ounces, pounds, and so on.
But just take the SI system as the official one, and you will have one basic unit for each quantity.
 
  • #9
Hexhunter,

Why don't you use miles to weigh yourself? And why don't you order a metre of milk? We have different units to quantify different types of measurement, although (as Dex pointed out) they are often related, and you can usually describe one unit (Volt, like on a battery, for example) in terms of other units.

Good luck with your GCSE, stick at it and if you can do an AS in Physics then you'll have a better chance of getting into uni!
 

1. Why are temperature measurements not typically measured in kilojoules (KJ)?

Temperature is not measured in kilojoules because kilojoules are a unit of energy, while temperature is a measure of the average kinetic energy of molecules in a substance. The most commonly used unit for temperature is the Kelvin (K), which is based on the absolute scale and is directly proportional to the average kinetic energy of molecules in a substance.

2. Why are voltage measurements not typically measured in kilojoules (KJ)?

Voltage is not measured in kilojoules because kilojoules are a unit of energy, while voltage is a measure of the electrical potential difference between two points. The most commonly used unit for voltage is the Volt (V), which is equivalent to one joule of energy per coulomb of charge.

3. Why is energy sometimes measured in kilojoules (KJ) instead of joules (J)?

Kilojoules are used to measure energy in larger quantities, while joules are typically used for smaller quantities. For example, food energy is often measured in kilojoules because it requires a large amount of energy to sustain human metabolism, while the energy required to light a light bulb is typically measured in joules.

4. Why do some scientific instruments measure temperature in degrees Celsius (°C) instead of Kelvin (K)?

Degrees Celsius and Kelvin are both units for measuring temperature, but they are based on different scales. While Kelvin is based on the absolute scale, where 0 K is absolute zero (the lowest possible temperature), degrees Celsius is based on the Celsius scale, where 0°C is the freezing point of water and 100°C is the boiling point of water. Degrees Celsius is more commonly used for everyday temperature measurements, while Kelvin is typically used in scientific calculations.

5. Why are some measurements given in both Celsius (°C) and Fahrenheit (°F) instead of just one unit?

Celsius and Fahrenheit are both commonly used temperature scales, with Fahrenheit being more commonly used in the United States and Celsius being more commonly used in the rest of the world. Some measurements may be given in both units to make it easier for people who are more familiar with one scale to understand the measurement in the other scale. This is especially useful when comparing temperatures between different regions or countries.

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