# CHAPTERS BY WACEK KIJEWSKI

# # Chapter 06 Conversion of Units

*It is a great nuisance that knowledge can be acquired by hard work.
*Somerset Maugham

The method presented below is based on knowledge of power of ten notation, knowledge of SI prefixes and manipulation of exponents. Once you have mastered these important skills, you will find out that this method employs logical steps that are easy to use in any combination of units. It is recommended instead of a unit factor method which is still widely used and which requires remembering unit factors. The unit factor method is inefficient and therefore, not suitable to use in more complex conversions encountered in physics.

The worked examples cover all possible forms of conversion from and to smaller, standard and larger SI units. It is advisable to do conversion in recommended steps in order to avoid mistakes. Later if you acquire a sufficient level of dexterity you may do two or more steps at a time to save time. However, please remember that correctness is a priority.

#### **Worked examples**

1. Conversion of a measurement expressed in:

a) a larger unit to its equivalent in a standard (basic or derived) unit,

b) a smaller unit to its equivalent in a standard unit.

Only one step is required in both of these cases.

Step 1: replace a prefix with its value.

E.g.1: 6.4 kV = 6.4 × 10^{3} V k = 10^{3}

E.g.2: 0.2 mA = 0.2 × 10^{-3} A m = 10^{-3}

Do you like anecdotes, interesting and challenging problems, fun facts, puzzles, jokes related to metric system and measurement? Read them in the 2006 on-line edition of "SI Units, Conversion and Measurement Skills",186 pp.