SI Units
International System of Units (SI)
The International System of Units is the modern metric system. It is abbreviated SI, from the original French “Le Système International d’Unités.”
Here’s an example of one of the most commonplace SI units -length in meters:
- Quantity name: Length
- Dimension symbol: L
- Unit name: meter
- Unit symbol: m
How is this used? One example would be if you are taking notes while measuring distances, it’s a lot easier to write L = 50 m than it is to write “the length is fifty meters”.
Here is a table of some of the common time and electric quantities and units you will use in these lessons.
| Quantity | Unit | Description | ||
|---|---|---|---|---|
| Name | Symbol | Name | Symbol | (non-technical version) |
| Time | t | second | s | This is seconds, the familar time measurement |
| Frequency | f | hertz | Hz | Repetitions per second |
| Current | I | amps or amperes | A | Flow of electrons |
| Voltage | e or V | volts | V | Electical pressure that makes current flow through circuits |
| Resistance | R | ohm | Ω | Resistance to electrtic current, which reduces the rate current flows through a circuit at a given voltage |
| Capacitance | C | farad | F | The amount of charge a device called a capacitor can store when boltage is applied to it |