#### Principles

##### Quantity, units and symbols
To avoid misunderstandings it is important to use the correct physical expressions.

 Physical quantity Symbol SI Unit Symbol Measurement device length l meter m ruler, caliper mass or weight m gram g scale pounds lb current I ampere A ammeter, clamp meter voltage V volt V voltmeter resistance R ohm Ω ohmmeter wattage, power P watt W wattmeter

Examples:  A current I is 2 A (Ampere).
The voltage V is 12 V (Volt).
The resistor R has 10 kΩ (kilo ohm). The resistor R13 in the circuit has
56 kΩ (kilo ohm).

##### SI Prefixes
In practice the values of measurements are often too big or too small to manage with the basic units only. The following prefixes are used in electronics:

 Prefix Symbol Factor Power of 10 giga G 1 000 000,000 109 mega M 1 000 000 106 kilo k 1 000 103 milli m 0.001 10-3 micro µ 0.000 001 10-6 nano n 0.000 000 001 10-9 pico p 0.000 000 000 001 10-12

Examples:      1 A = 1 000 mA
100 kΩ = 100 000 Ω (or 0.1 MΩ)
97.6 MHz = 97 600 kHz (or 97 600 000 Hz)
100 nF = 0.1 µF (or 100 000 pF)

##### Usage
When converting a unit or a formula write down all steps carefully.
Do not do it mental! A 0 is lost and a . is put at a wrong place easily.

-  Learn the sequences. For numbers which are bigger than the units: kilo – mega – giga
and for number smaller than the unit: milli – micro – nano – pico
-  Remember that the steps between the following or the previous prefix is the
factor 1 000
-   During converting the value remains the same. When the prefix gets bigger
(mega instead of kilo) the number must get smaller (1 instead of 1 000)

Examples:  1 A = ? mA
the difference of A to mA is 1 000
mA is smaller than A. So the number must get bigger (x 1 000)
1 A = 1 000 mA

2.2 KΩ = ? Ω
the difference of KΩ to Ω is 1 000
Ω is smaller than KΩ. So the number must get bigger (x 1 000)
2.2 KΩ = 2 200 Ω

3 000 V = ? kV
the difference of V to kV is 1 000
K is bigger than V. So the number must get smaller (/ 1 000)
3 000 V = 3 kV

94.5 MHz = ? Hz
the difference of M to the Hz is 1 000 000 (kilo is in between)
Hz is smaller than MHz. So the number must get bigger (x 1 000 000)
94.5 MHz = 94 500 000 Hz (or 94 500 kHz)

##### Exercises
To see the answer just the space in front of the target value.

1 000 V =                  1 KV

1 000 mV =                1 V

2.2 KΩ =              2 200

3.3 MΩ =             3 300 KΩ

250 mV =               0.25 V

25 mV =               0.025 V

545 V =               0.545 KV

11 KV =              11 000 V

11 KV =        11 000 000 mV

500 µA =                 0.5 mA

50 µA =                 0.05 mA

50 µA =           0.000 05 A

0.230 KV =              230 V

220 nF =               0.22 µF

10 000 µF =             10 mF

10 000 µF =  10 000 000 nF

22 pF =               0.022 nF