What are the SI units?
- mass: kg (kilograms)
- length: m (metres)
- time: s (seconds)
- amount of substance: mol (moles)
- temperature: K (kelvin)
- electric current: A (amperes)
- light intensity - cd (candela)
Prefixes from 10^12 to 10^-15
Tera - 10^12 - T
Giga - 10^9 - G
Mega - 10^6 - M
Kilo - 10^3 - k
centi - 10^-2 - c
milli - 10^-3 - m
micro - 10^-6 - µ
nano - 10^-9 - n
pico - 10^-12 - p
femto - 10^-15 - f
What are random errors and how do you reduce the effect of them?
- errors that affect precisions
Reduce with: - take repeats and calculate means to identify anomalies
- using digital equipment to reduce human error and have smaller intervals
- use appropriate equipment
What are systematic errors and how to reduce them?
- Systematic errors occur due to apparatus or faults in method
- affect accuracy as all results affected by it
Reduce with: - calibrate equipment (zero error)
- use digital measuring equipment
- use appropriate equipment
What is absolute and percentage uncertainty?
Uncertainty: the bounds in which the two bounds lie
- Absolute: uncertainty as a fixed quantity
- Percentage: uncertainty as percentage of measurement
How to tell uncertainty when not quoted?
For instruments with 2 judgments at the start and end (e.g. ruler), the uncertainty is +- the smallest increment.
For instruments with 1 judgement (e.g. top-pan balance), uncertainty is +- half of the smallest increment.
What is uncertainty in a range of values?
- it is +- half of the range centred around the mean
How to display uncertainties in graphs? How can you use this to find percentage uncertainty in gradient?
- Error bars extending from our point
- The percentage uncertainty can be found from the percentage difference between the best and worst gradient using the top and bottom of the first and last error bars
How do uncertainties work when values are added or subtracted?
The absolute uncertainties are added as well for the result.
How do uncertainties work when values are multiplied or divided?
The percentage uncertainties are added which can then be converted to the absolute uncertainties.
How do you use orders of magnitude?
Powers of 10 are orders of magnitude, they can be used in standard form
How to use estimation and why is it used?
- approximate values of physical quantities
- can be used for comparison or to check if a value is reasonable
