Physics deals with very large and very small values, so SI units are used with prefixes that multiply the unit by a power of ten. The prefixes you need for AQA are:• tera (T): 1012
• giga (G): 109
• mega (M): 106
• kilo (k): 103
• centi (c): 10−2
• milli (m): 10−3
• micro (μ): 10−6
• nano (n): 10−9
• pico (p): 10−12
• femto (f): 10−15Take care with the case of the letter: M (mega, 106) and m (milli, 10−3) differ by a factor of 109.To use a value in an equation, replace the prefix by its power of ten.Worked example 1: a capacitor is 470 nF.470 nF = 470 × 10−9 F = 4.70 × 10−7 F Worked example 2: write 0.035 MW with a more suitable prefix.0.035 × 106 W = 35 000 W = 35 × 103 W = 35 kW Choose a prefix that gives a number between about 1 and 1000. Other examples: the radius of a nucleus is a few fm, visible light has wavelengths of 400 to 700 nm, and a WiFi signal has a frequency of 2.4 GHz.Remember that the kilogram, not the gram, is the base unit of mass, so 1 g = 10−3 kg.
• giga (G): 109
• mega (M): 106
• kilo (k): 103
• centi (c): 10−2
• milli (m): 10−3
• micro (μ): 10−6
• nano (n): 10−9
• pico (p): 10−12
• femto (f): 10−15Take care with the case of the letter: M (mega, 106) and m (milli, 10−3) differ by a factor of 109.To use a value in an equation, replace the prefix by its power of ten.Worked example 1: a capacitor is 470 nF.