An Introduction to the units used in Physical Measurement

1. Topic 1 – Physical Measurements 1.2a – The SI Units

3. All other units can be derived from these 7.

6. The second (quantity time [T], symbol s) – originally defined as 1/86400 of a mean solar day it is now defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

11. Newton is the unit of force

12. Force = mass x acceleration (amongst others)

13. [N] = [kg] x [ms -2 ]

14. N = kgms -2 Derived units

16. Concentration

17. Frequency

18. Power

19. Pressure

20. Electric Charge

21. Voltage

25. This makes it easier to read values in reports etc.

26. In general use scientific notation in results tables and intermediate work (as this makes working with large numbers much easier) and use prefixes for the final answer.

27. SI Prefixes Name Symbol Exponent Multiplier Peta P 10 15 1 000 000 000 000 000 Tera T 10 12 1 000 000 000 000 Giga G 10 9 1 000 000 000 Mega M 10 6 1 000 000 Kilo k 10 3 1 000 10 0 1 milli m 10 -3 0.001 micro μ 10 -6 0.000 001 nano n 10 -9 0.000 000 001 pico p 10 -12 0.000 000 000 001 femto f 10 -15 0.000 000 000 000 001

29. 150 564 kL

30. 0.003 672 nF

31. 178.3671 μ C

32. 258 245 mK