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You will find that the following units and symbols are commonly encountered in electrical circuits. It is important to get to know these units and also to be able to recognize their abbreviations and symbols.
| Unit | Abbreviation | Symbol | Definition |
|---|
| Ampere | A | I | Unit of electric current (a current of 1A flows in an electrical conductor when a charge of 1C is transported in a time interval of 1s) |
| Coulomb | C | Q | Unit of electric charge or quantity of electricity (a charge of 1C is transported through an electrical conductor in a time interval of 1s when a current of 1A flows in it) |
| Farad | F | C | Unit of capacitance (a capacitor has a capacitance of 1F when a charge of 1C results in a potential difference of 1V across its plates) |
| Henry | H | L | Unit of inductance (an inductor has an inductance of 1H when an applied current changing uniformly at a rate of 1A/s produces a potential difference of 1V across its terminals) |
| Hertz | Hz | f | Unit of frequency (a signal has a frequency of 1Hz if one complete cycle occurs in a time interval of 1s) |
| Joule | J | E | Unit of energy (1J of energy is required to move a force of 1N through a distance of 1m) |
| Ohm | Ω | R | Unit of resistance (an electrical conductor has a resistance of 1 ohm when a current of 1A produces a potential difference of 1V across it) |
| Second | s | t | Unit of time (this is a fundamental unit) |
| Siemen | S | G | Unit of conductance (the reciprocal of resistance) |
| Tesla | T | B | Unit of magnetic flux density (a flux density of 1T is produced when a flux of 1Wb is present over an area of 1 square metre) |
| Volt | V | V | Unit of electric potential (a potential difference of 1V appears across a resistance of 1 ohm when a current of 1A is flowing in it) |
| Watt | W | P | Unit of power (equal to 1J of energy consumed in a time of 1s) |
| Weber | Wb | Φ | Unit of magnetic flux (a potential difference of 1V will appear across the ends of an electrical conductor when it moves at a uniform rate in 1 second through a magnetic flux of 1Wb) |
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