Core Practicals Flashcards
Explain the method to determine ‘g’
Drop an object from rest. Measure time and distance until it reaches the ground. Use suvat to determine g.
How can you graphically determine ‘g’
2s over t^2. Gradient = g
How can you improve accuracy for finding ‘g’?
Use light gates or a trap door for timing rather than a stopwatch, to eliminate human reaction times, which cause a % uncertainty.
What systematic errors are there when determining g?
Air resistance, will cause the measured value of g to be less than the true value.
Explain the method for determining the resistivity of a wire
Set up a wire connected to a cell with a ammeter and voltmeter parallel to the wire.
Measure the length of wire and numerous diameters. Measure voltage and current to calculate resistance - V=IR.
What systematic errors are there when determining the resistivity of a wire?
Heating of wire due to current. Using a small current can minimise this. Resistivity is temperature dependant.
How do you calculate percentage uncertainty?
uncertainty/mean value x 100%
Explain what graph you may plot for determining resistivity.
R against l and gradient = ρ/A
Define Validity
A measurement is valid if it measures what it is supposed to
Define Systematic Error
Introduces the same error to all measurements. Includes zero errors.
Define Random Error
Reading might be too small or large by the same amount.
Explain how you would combine uncertainties
If adding data: add absolute uncertainties
If multiplying data: add percentage uncertainties
Raised to a power: Multiply U% by power
Define error
An error is the difference between the (measured) result and the
true value
Define uncertainty
An uncertainty is the interval/range in which the (true) value can
be considered to lie
Give two reasons why a measurement may have an uncertainty.
- resolution of instrument
- zero error
- parallax error
- reaction time
