Flashcards in Paper 3 Deck (26):
What is the definition of validity?
A measurement is valid if it measures what its supposed to measure
What is the definition of true value?
The value that would be obtained in an ideal experiment
What is the definition of accuracy?
A measurement is accurate if its judged to be close to the true value
What is the definition of precision?
The consistency (closeness) between results by a repeated experiment
What is the definition of repeatability?
The judged precision of the results obtained by using the same method and apparatus
What is the definition of reproducibility?
The judged precision of the results obtained by using different apparatus and/or method
What is the definition of uncertainty?
The interval within which the true value can be expected to lie with a given level of confidence or probability
What is the definition of error?
The difference between the measured value and the true value
What is the definition of resolution?
the smallest measuring interval
What are common control variables?
Time, Temperature, Mass, Position, Motion, Friction
What is parallax error?
A change in the apparent position of an object relative to more distant objects, caused by a change in the observer's line of sight toward the object
What is a zero error?
It is when an instrument gives a reading when the true reading at that time is zero.
What happens in the experiment investigating the absorption of gamma radiation by lead?
-You place lead between a gamma source and a geiger muller tube (work out background count first)
-Vary the thickness of the lead an take measurements
-Plot lnA=lnA' - μx
What happens in the experiment investigating Boyles law?
-Use a pump to increase the pressure inside a tube to its max value
-Release pressure to see that the volume increases
-Plot P against 1/V and the gradient is NkT
What happens in the experiment investigating specific heat and latent heat?
-Ice at 0℃ is added to water of known mass and temperature
-Assume the temperature decrease in water is temperature increase for the ice
What happens in the experiment calibrating a thermistor?
-The thermistor is connected to circuit with a cell and another resistor with a voltmeter connected in parallel
-Measure temperature and voltage across the resistor
-Use potential divider equation to work out resistance of thermistor
What happens in the experiment determining EMF and internal resistance?
-Use a circuit with a variable resistor in, connect an ammeter in series and a voltmeter across the cell
-Plot V= E - Ir (V against I)
What happens in the experiment determining resistivity?
-Use a circuit with a wire in, and a voltmeter which can vary it's length
-measure current and voltage for different lengths and work out resistance
-Then plot R against L and the gradient x area equals resistivity
What happens in the experiment determining the Youngs modulus of a material?
-Measure the mass of the load to get the force on the wire, measure the original length and extension, measure the diameter in multiple places
- E = (Fx)/(△xA)
-Plot F against △x, the gradient times x/A will, give Youngs modulus
What happens in the experiment determining the speed of sound?
-Move a microphone connected to a oscilloscope between a loudspeaker and reflector
-Measure the distance between the flat lines on the oscilloscope which equals λ/2
-Plot λ against 1/f and the gradient is the speed of sound
What happens in the experiment determining the speed of a wave on a string?
-Hang a load on the end of the string which acts as tension and attach a vibrator to the other end
- f =(1/2L)(√T/√µ) v = √T/√µ
What happens in the experiment determining g?
-Drop a piece of card through two light gates and measure the time it takes and the distance between
-Use 2s/t = at + 2u to get a gradient of a and intercept of 2u
What happens in the experiment determining viscosity?
-Drop a ball bearing in an unknown liquid and measure the time it takes travelling at terminal velocity between two lines
- W = u + F because its at terminal velocity
What happens in the experiment measuring wavelength?
-Point a laser through a diffraction grating and measure the distance between maxima and the angle from the centre maxima
- tan⏀ = x/D D is the distance between laser and wall
nλ=dsin⏀ n is the order of maxima
d is the distance between gratings
What happens in the experiment confirming F=ma?
-Attach a trolley to a string with hanging masses, place an interrupt card on top of the trolley since it will go through light gates
-Measure the the change in velocity and time, take masses off the load and place them on the trolley to conserve mass