**Ohm’s Law**

Probably the most important law in electronics is Ohm’s Law. Ohms Law states that the voltage across a resistor equals the resistance of the resistor times the current flowing through it (V=R*I). Thus if you have a resistance of 1000 ohms and a current of 10 milliamps flowing through it, the voltage over it will be: 1000 * 0.01=10V. Ohms law can be expressed in the following ways:

V | = R * I |

R | = V / I |

I | = V / R |

To see some basic examples of Ohms law, browse to the resistors section.

**Precision**

It is usually not necessary to be very precise in the calculation of the values, thus I will use approximations most of the time. The reason is that the components we normally use have quite a wide tolerance, e.g. the resistors will mostly be 5% and capacitors about 20%. Thus you can see that using values correct up to 10 digits is just a waste of time.

**Notation**

Here is a summary of commonly used values for electronic components:

Abbreviation | Name | Value |

p | pico | 0.000 000 000 001 (1e-12) |

n | nano | 0.000 000 001 (1e-9) |

u | micro | 0.000 001 (1e-6) |

m | milli | 0.001 (1e-3) |

K | kilo | 1 000 (1e3) |

M | mega | 1 000 000 (1e6) |

G | giga | 1 000 000 (1e9) |

For the components that most hobbyist will use, you will see kilo and mega used for resistors; pico, nano and micro for capacitors and micro and milli for inductors.

**Shorthand notation**

Here are a few guidelines used in industry to write the values of components:

- The value of a capacitor ends with an F (Farad)
- The value of an inductor ends with an H (Henry)
- The value of a resistor ends with an R if smaller than 1000 Ohm, otherwise it is omitted
- Instead of a comma for a resistor of say 4,7 kilo Ohm, use the ‘K’ to indicate the comma (4K7)

A few examples:

A resistor of 10 000 Ohm | 10K |

A resistor of 4 700 000 Ohm | 4M7 |

A resistor of 1 Ohm | 1R |

A resistor of 0.25 Ohm | 0R25 |

A capacitor of 0.004 700 Farad | 4700uF |

An inductor on 0.010 Henry | 10mH |