2 Chapter 1 • Dynamics
Te following points will prove helpful in the correct usage of symbols and abbreviations. • Symbols should be used only when theirmeaning is clear. • Full stopsmay be omitted inmulti-word abbreviations, for example; e.m.f. or emf, p.d. or pd, A.C. or AC, a.c. or ac, D.C. or DC and d.c. or dc.
• In a compound unit symbol, a full stop denotesmultiplication, e.g. N.m (the full stop may also be leſt out, e.g. Nm), and a forward slash (/) symbolises division, e.g. m/s (metres per second) or 3/4 (3 ÷ 4).
• A unit symbol should be used only after a numerical value, e.g. 5 kg, 10 Nmand 12 A. • A unit symbol is the same for the singular and plural, e.g. 1 kg or 5 kg and 1 V or 12 V.
It is common practice to differentiate between two or more similar quantity symbols by using numerals or letters placed aſter and lower than the symbol, e.g.: d1 : d2 (different diameters) RP (resistance of parallel circuit) a1 : a2 (different areas) RS (resistance of series circuit)
Small and capital letters are also oſten used, e.g.: d : D (different diameters) a : A (different areas)
Symbols such as: µ (micro, i.e. × 1–6) m(milli, i.e. × 10–3) (centi, i.e. × 10–2) k (kilo, i.e. × 103) M(mega, i.e. × 106)
are oſten used in front of unit symbols to abbreviate a numerical value, e.g.: 0,000 000 017Ωm or 0,017 × 10–6Ωm becomes 0,017 µΩm 0,003 V 0,45m
54 500m 7 550 000 J
or 3 × 10–3 v or 45 × 10–2 m or 54,5 × 103 m or 7,55 × 106 J
becomes 3 mV becomes 45 cm becomes 54,5 km becomes 7,55 MJ
Numerous errors occur due to incorrect units being used. Table 1.2 shows examples of correct conversions.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140