### Theory:

The following are the rules and conventions for writing SI Units and their symbols:
• The units named after scientists are not written with an initial capital letter.
Example: newton, henry, ampere and watt.

• The symbols of the units named after scientists should be written by the initial capital letter.
Example: N for newton, H for henry, A for ampere and W for watt.

• Small letters are used as symbols for units not derived from a proper noun.
Example: m for metre, kg for kilogram.

• No full stop or other punctuation marks should be used within or at the end of symbols.
Example: 5 m, and not as 5 m. or 5.m

• The symbols of the units are not expressed in plural form.
Example: 100 kg, not as 100 kgs.

• When the temperature is expressed in kelvin, the degree sign is omitted.
Example: 383 K, not as 383° K (If expressed in celsius scale, degree sign should be included, e.g. 100 °C, not as 100 C and 108 °F, not as 108 F).

• Use of solidus (/) is recommended for indicating a division of one unit symbol by another unit symbol. Not more than one solidus is used.
Example$m{s}^{-1}$ or m/s. J/K/mol should be $J{K}^{-1}{\mathit{mol}}^{-1}$

• The number and units should be separated by a space.
Example: 15 $\mathit{kgm}{s}^{-1}$ not as 15$\mathit{kgm}{s}^{-1}$

• Accepted symbols alone should be used.
Example: Ampere should not be written as amp, and second should not be written as sec

• The numerical values of physical quantities should be written in scientific form.
Example: The density of mercury should be written as $1.36\phantom{\rule{0.147em}{0ex}}×\phantom{\rule{0.147em}{0ex}}{10}^{4}\phantom{\rule{0.147em}{0ex}}\mathit{kg}{m}^{-3}$, not as $13600\phantom{\rule{0.147em}{0ex}}\mathit{kg}{m}^{-3}$