Читать книгу The ESD Control Program Handbook - Jeremy M. Smallwood - Страница 17

In electrostatics and ESD work, we often have to deal with very large or very small numbers. For example, the resistance of a material may be measured to be 10 000 000 000 Ω. For convenience and clarity, we use scientific notation and SI unit prefixes as shorthand for numbers (http://physics.nist.gov/cuu/Units/prefixes.html).

In scientific notation, the number is rewritten in the form a × 10^b, where a lies between 1 and 10, and b is the number of decimal places a must be shifted to get the full number. This is probably most easily understood by examples of resistance and capacitance (Table 1.1). Sometimes, when the number a is simply 1, it is omitted.

Table 1.1 Examples of use of scientific notation and SI prefixes.

Value	Scientific notation	SI prefix
150 Ω	1.5 × 102 Ω	150 Ω
22 000 Ω	2.2 × 104 Ω	22 kΩ
35 000 000 Ω	3.5 × 107 Ω	35 MΩ
1 000 000 000 Ω	1.0 × 109 Ω or 109 Ω	1 GΩ
1 000 000 000 000 Ω	1.0 × 1012 Ω or 1012 Ω	1 TΩ
0.000 022 F	2.2 × 10−5 F	22 μF
0.000 000 001 F	1.0 × 10−9 F or 10−9 Ω	1 nF
0.000 000 000 15 F	1.5 × 10−10 F	150 pF
0.000 000 000 001 F	1.0 × 10−12 F	1 pF