Definition:SI/Energy
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Definition
Various SI units of energy which have specific names are as follows:
Joule
The joule is the SI unit of energy.
It is defined as being:
- the energy transferred to (or work done on) a body when a force of $1$ newton acts on that body in the direction of the force's motion through a distance of $1$ metre
- the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second.
Thus:
- $1 \, \mathrm J = 1 \, \mathrm N \, \mathrm m$
| \(\ds \) | \(\) | \(\ds 1\) | joule | |||||||||||
| \(\ds \) | \(=\) | \(\ds 10^7\) | ergs |
Megajoule
The megajoule is an SI unit of energy.
| \(\ds \) | \(\) | \(\ds 1\) | megajoule | |||||||||||
| \(\ds \) | \(=\) | \(\ds 10^6\) | joules |
Kilowatt-Hour
The kilowatt-hour is an SI unit of energy.
It is defined as being:
| \(\ds \) | \(\) | \(\ds 1\) | kilowatt-hour | |||||||||||
| \(\ds \) | \(=\) | \(\ds 10^6\) | milliwatt-hours | |||||||||||
| \(\ds \) | \(=\) | \(\ds 3 \cdotp 6\) | megajoules | |||||||||||
| \(\ds \) | \(=\) | \(\ds 3 \cdotp 6 \times 10^6\) | joules |
Milliwatt-Hour
The milliwatt-hour is an SI unit of energy.
It is defined as being:
| \(\ds \) | \(\) | \(\ds 1\) | milliwatt-hour | |||||||||||
| \(\ds \) | \(=\) | \(\ds 3 \cdotp 6\) | joules |
Electron Volt
The electron volt is a SI unit of energy.
It is defined as:
- the amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of $1$ volt in a vacuum.
| \(\ds \) | \(\) | \(\ds 1\) | electron volt | |||||||||||
| \(\ds \) | \(=\) | \(\ds 1.60217 \, 6634 \times 10^{−19}\) | joule | \(\quad\) (exact) |