Flashcards in Paper 3 Deck (26):

1

## What is the definition of validity?

### A measurement is valid if it measures what its supposed to measure

2

## What is the definition of true value?

### The value that would be obtained in an ideal experiment

3

## What is the definition of accuracy?

### A measurement is accurate if its judged to be close to the true value

4

## What is the definition of precision?

### The consistency (closeness) between results by a repeated experiment

5

## What is the definition of repeatability?

### The judged precision of the results obtained by using the same method and apparatus

6

## What is the definition of reproducibility?

### The judged precision of the results obtained by using different apparatus and/or method

7

## 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

8

## What is the definition of error?

### The difference between the measured value and the true value

9

## What is the definition of resolution?

### the smallest measuring interval

10

## What are common control variables?

### Time, Temperature, Mass, Position, Motion, Friction

11

## 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

12

## What is a zero error?

### It is when an instrument gives a reading when the true reading at that time is zero.

13

## 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

14

## 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

15

## 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

16

## 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

17

## 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)

18

## 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

19

## 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

20

## 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

21

## 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

22

## 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

23

## 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

24

## 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

25

## 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

26