Practical Skills At AS-level Flashcards
Key 🗝 ideas 💡, definitions ND formulae
Name the 6 base(as level) quantities and their corresponding units
- Mass, unit: kilogram (Kg)
- Time, unit: seconds (s)
- Thermodynamic temperature, unit: Kelvin (K)
- Distance, unit: metres (m)
- Current, unit: Amperes (A)
- Amount of substance, unit : moles (mol)
Define derived units ?
Are a combination of base units
Definition of SI units :
They are carefully defined units that are used throughout the scientific world for measuring all quantities.
Definition of base quantities :
Are the fundamental quantities whose units are used to derive to derive all other units
Definition base units :
Are the units of base quantities. The fundamental units.
Homogeneity of equations refers to:
The units on both sides of the equation must be the same
What are the 10 sub - /multiples and their multiplying factor… Starting from smallest to biggest.
Pico (p) = 10^ - 12
Nano (n) =10^-9
Micro (u) =10 ^-6
Milli (m) =10 ^-3
Centi (c) =10 ^-2
Deci (d) =10 ^-1
Kilo(K) =10 ^3
Mega (M) =10 ^6
Giga (G) =10 ^9
Tera (T) =10 ^12
What are the two types of errors :
And an example of each
- Random e.g. Parallax error
2 systematic e.g. Zero error
There characteristics of random errors :
- Due to the observer
- Cannot be eliminated
- Can be reduced by e.g. Taking 5 or more readings and averaging or repeating the experiment to get more results
4 characteristics of systematic errors :
- Due to faulty equipment or apparatus
- this is constant ; it affects all measurements by the same magnitude
- It cannot be reduced but it can be eliminated by taking the equipment to the manufacturer
- With a systematic error your results can be precise but they will not be accurate
Definition of accuracy :
Refers to how close a measurement is to the true value
Definition of precision :
Refers to how the close the measurements are to each other (or how close they are to the range of measurements /values)
What does A and B stand for in the measured quantity :
A +- B
A= measured value
B= absolute uncertainty
Formula for percentage uncertainty =
(Absolute uncertainty /measured value) ×100
Formula for fractional uncertainty :
Absolute uncertainty /measured value
Formula for absolute uncertainty =
Fractional uncertainty × Calculated value
The 3 rules of combining uncertainties:
- For similar quantities whether the quantities are added/subtracted from each other - their absolute uncertainties are always added (e.g. Cm and cm)
- For different quantities ; we have to add the fractional/percentage uncertainties
- When you calculate the uncertainty in a quantity that has a power ; you must multiple the percentage /fractional uncertainty of the quantity by its power
3 things can be used to measure length :
- A metre rule
- vernier caliper (diameters in hollow tubes)
- Micrometre screw gauge
What 2 things measure weight:
- Top pan balance
2. Spring balance
What can be used to measure angles
Protractor
What two things can be used to measure time intervals?
- A clock
2. Stopwatch
What 2 things can be used to measure potential difference?
- Voltmetre
2. Cathode ray oscilloscope
What can be used to measure time intervals and frequencies of waves?
A cathode ray oscilloscope with calibrated time base
What can be used to measure temperature?
A thermometer
