very important information for paper 3

Define a systematic uncertainty and give 2 examples of when these would happen

Uncertainties that consistently skew measurements in the same wrong direction

Examples: Calibration error, Zero error

What is a zero error? Give an example

When a measuring device displays a value when there shouldnt be any, for example when a weighing scale displays a value when theres no load on it

Why would a systematic error occur? (2 things)

1. Faults in apparatus

2. Faults in experimental method

Give an example of a random error

Electronic noise in circuits

Define a random uncertainty and give 2 examples of when these would happen

Uncertainties that cause measurements to fluctuate around the true value

Examples: Failing to keep control variables constant, human error in reading intruments

How can the effect of random uncertainties be reduced

Taking a mean

A device that doesnt require you to line up with 0 to take a measurement is called what?

A reading

A device that requires you to line up with 0 to take a measurement is called what?

A measurement

What is the uncertainty of Readings?

½ Resolution

What is the uncertainty of Measurements?

Equal to the Resolution

Define resolution

Smallest increment of an experimental instrument

Give 4 examples of experimental instruments that take Readings

1. Thermometer

2. Digital voltmeter/ammeter

3. Micrometer

4. Balance

What is the absolute uncertainty?

Half the uncertainty

Give 3 ways you can minimise random errors

1. Take a mean

2. Use computers/Data loggers to reduce human error

Why is using computers/data loggers/cameras better than humans?

Smaller resolution therefore more accurate, and less likely to make human errors

What is a parallax error?

A type of human error where their eye is not aligned perpendicularly to the measuring scale, producing an incorrect reading

How would you reduce systematic errors in a radiation experiment?

Measure background radiation before the experiment and remove it from the final result

How can you reduce the uncertainty of a ruler?

Fixing one end of it to something

If you are adding or subtracting data, what should be done with the uncertainties?

Add the absolute uncertainties

If you are multiplying or dividing data, what should be done with the uncertainties?

Add percentage uncertainty

How do you find percentage uncertainty?

(uncertainty/value)x100

If you are raising the data to a power, what should be done with the uncertainty?

Multiply by the power

What are uncertainties shown as in graphs?

Error bars

How should a line of best fit interact with error bars in a graph

Must pass through all of them

How do you find the uncertainty in a gradient? (2 steps)

1. Draw a line of best and worst fit and a line of best fit if you need to

2. The uncertainty is the difference between them, so you do (LOBF - LOWF)/(LOBF)x100

How do you draw a line of worst fit?

Draw a line from the bottom of the bottom error bar to the top of the top error bar

What should you do if the line of best fit and the line of worst fit have different Y-intercepts?

Find the uncertainty in the Y-intercept

How do you find the uncertainty of the Y-intercept?

(LOBF y-intercept - LOWF y-intercept)/(LOBF y-intercept)x100

Which variable goes on each axis of a graph?

Y - dependent
X - independent

How should you draw a line of best fit on a curved line graph?

Draw a smooth curve with about half the points on each side of it

For a relationship where y = k/x how do you make it a straight line graph?

the reciprocal
y against 1/x

How would you plot a logarithmic or exponential function as a straight line?

Put it into the form y = mx + c using log laws

logy² is the same as what?

2logy

log(x/y) is the same as what?

logx - logy

loga(xy) is the same as what?

logax + logay

Independent variable

The one that is changed

Dependent variable

One being measured

How would you prove and disprove x and y are inversely proportional?

multiply each data point together, if the result is constant they are inversely proportional

How would you prove and disprove x and y are proportional ?

Check if the ratio y/x is constant for all data points

What is Boyles law?

V is inversely proportional to pressure

What axis does the independent variable ALWAYS go on?

X-axis

What axis does the dependent variable ALWAYS go on?

Y-axis