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
What can be used to measure current?
Ammeter
Rulers measure to the nearest…
Millimetre
Vernier calipers measure to the nearest
0.1 mm
Micrometres measure to the nearest
0.01 mm
vernier calipers have what 2 scales?
- A main scale measures in mm
2. A vernier scale measure in 0.1mm
Read pg 15 on physics revision guide to understanding how a micrometre screw gauge works
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