Practical skills

• Si units are the fundamental units and include: mass (kg), length (m), time (t), moles (mol), temperature (K), current (A) and candela (cd).
• Kilo is 10^3, mega is 10^6, giga is 10^9, tera is 10^12.
• Centi is 10^-2, milli is 10^-3, micro is 10^-6, nano is 10^-9, pico is 10^-12, femto is 10^-15.
• 1 ev = 1.6 x10 ^ -19 J.
• 1 kWh = 3.6 x10 ^ 6 J.
• Random errors affect precision and can be reduce by taking repeats and calculating a mean.
• Systematic errors affect accuracy and can be reduced by calibrating results or reading a result off at eye - level.
• The uncertainty in a reading is +/- half the smallest division.
• The uncertainty in a measurement is at least +/- 1 smallest division.
• For repeated data, the uncertainty is half the range.
• When adding or subtracting data, add absolute uncertainties.
• When multiplying or dividing data, add percentage uncertainties.
• When raising data to a power, multiply percentage uncertainty by that power.
• Percentage uncertainty can be found from a graph by finding the best and worst gradient using line of best fit with error bars and then subtracting them from each other and dividing by the best gradient.