0.0 Practical Skills Flashcards
How do you design an experiment?
1) Make a prediction.
2) Decide what data to collect and how you will do it.
3) Identify the independent, dependent, and control variables.
4) Select appropriate equipment.
5) Do a risk assessment and plan any safety precautions.
6) Write out a clear method.
What is a variable?
A quantity that can be changed.
What is an independent variable?
The thing you are in charge of changing.
What is a dependent variable?
The thing you measure.
What is a control variable?
The things you keep the same.
What is a hazard?
Anything that can cause harm.
What is a risk?
How someone can be harmed by a hazard.
What is a prevention?
How to stop someone being harmed.
How does a micrometer work?
By placing an object between the anvil and spindle. Turning the ratchet to close the spindle.
What is the benefit of having a ratchet?
It prevents you from squashing the object and distorting the measurement.
What is the main scale on a micrometer?
A main scale that does not rotate and is marked every 1/2 mm.
What is the rotating scale on a micrometer?
A rotating scale that rotate and is marked with 50 divisions.
What will a full rotation of the rotating scale do?
Cover or uncover a 1/2 mm (0.01 x 50) line in the main scale.
How do you use a micrometer?
1) Look to see what line has just been uncovered on the main scale.
2) Look to see what number on the rotating scale lines up with the horizontal line on the main scale.
3) Add the main scale and rotating scale reading together.
What are the benefits of using a caliper?
- You can use the lower jaws and close them like a micrometer.
- Or you can use the upper jaws to measure the internal diameter of an object.
What is the downside of using a caliper?
There is no ratchet to prevent squashing the object.
What is the main scale of a caliper alike?
A ruler with markings every mm.
What is the movable scale that can slide left or right known as?
A vernier scale
If the vernier scale has 10 divisions what is the level of precision it can read to?
0.1mm (1mm/10)
If the vernier scale has 20 divisions what is the level of precision it can read to?
0.05mm (1mm/20)
How do you use a caliper?
1) Look to see where 0 is on the vernier scale.
2) The vernier scale is a ‘zoomed-in’ version of 1mm.
3) Next look to see where a line on the vernier scale matches up exactly with a line on the main scale.
4) Add this to your main scale reading.
What are the four types of data?
- Discrete data
- Continuous data
- Categoric data
- Ordered data
What is discrete data?
Discrete data is only a set number, like shoe size (cannot be 12.7654)
What is continuous data?
You can have any value, you can never measure the exact value, like current or voltage.
What is categoric data?
A variable that can be put into categories, like types of material: wood, glass, etc.
What is ordered data?
Similar to categoric but can be put in order, for example, risk can be low, medium, high, etc.
Why is plotting graphs important?
It allows us to visually see how two variables link.
What do correlations indicate?
Correlation indicates a relationship between two variables.
If the equation of a straight line includes an exponential function, what type of logs do you use?
Natural logs
If the equation of a straight line includes powers, what type of log do you use?
Log to the base 10
What is the first rule when using logs?
ln(e^x) = x
What is the second rule when using logs?
ln(ab) = ln(a) + ln(b)
What is the third rule when using logs?
ln(a/b) = ln(a) - ln(b)
What is the fourth rule when using logs?
ln(a^b) = b ln(a)
What is an error?
The difference between the measured value and the expected value of something.
What is an uncertainty?
An uncertainty is a way of expressing or summarising the error.
What is a mistake?
A mistake is simply not doing something correctly through carelessness.
What does it mean to be accurate?
It means your measurement is close to the true value.
What does it mean to be precise?
This means that the spread of your values is very small.
What are the two types of error?
Systematic error and random error
What are systematic errors?
These are errors that affect all measurements by the same amount.
How do you reduce systematic errors?
Make sure that all equipment is reading zero when it should (calibrated)
What are random errors?
These are errors that affect all measurements by different amounts.
How do you reduce random errors?
Take repeat readings to let you spot anomalies and remove them.
Also taking an average will help ‘smooth’ out your results.
What is human error an example of?
Random error
- Try to remove the need for a human to do any measuring.
What is a parallax error an example of?
Random error
- This is caused when your eye, the object you are measuring, and the measuring device are not lined up correctly.
- This can be eliminated by using a set square or by placing the object directly onto the measuring device.
What is calibration error an example of?
Systematic error
- This is caused when you do not check equipment is reading zero when it should be.
- This can be eliminated by either checking it reads zero when it should be or measuring something of a known size.
What is an uncertainty in a reading?
This is when you look at a piece of equipment once to make your judgment.
+ or - 1/2 the smallest division.
What is an uncertainty in a measurement?
This is when you look at a piece of equipment twice to make your judgment.
+ or - 1 the smallest division
What is an uncertainty in digital meters?
This is when you are using a device with a digital display.
+ or - 1 smallest division
What is an uncertainty in exam data?
This is when you are just presented with data but you don’t know how it was measured or what it was.
+ or - 1 is the least significant digit.
What is the equation for percentage uncertainty?
Percentage uncertainty = (Absolute uncertainty / Reading) x 100
How do you reduce percentage uncertainty and improve the experiment?
1) Make absolute uncertainty as small as possible.
2) Make the reading as big as possible.
How do you make the absolute uncertainty smaller?
Use higher precision equipment.
How do you make the reading bigger?
Measure a larger value, e.g. measure 10 oscillations of a pendulum not just 1.
When you add two measurements what happens to the absolute uncertainties?
You add the absolute uncertainties.
When you subtract two measurements what happens to the absolute uncertainties?
You add the absolute uncertainties.
When you multiply two measurements what happens to the percentage uncertainties?
You add the percentage uncertainties.
When you divide two measurements what happens to the percentage uncertainties?
You add the percentage uncertainties.
When you raise a value to a power what happens to the percentage uncertainties?
You multiply the percentage uncertainty by the power.
Do constants have uncertainty?
No
If the percentage difference is smaller than the percentage uncertainty, is the thoeory supported by the results?
Yes
If the percentage difference is bigger than the percentage uncertainty, is the thoeory supported by the results?
No
What does precise results mean?
The smaller the amount of spread of your data from the mean, the more precise it is. Precision only depends on the amount of random error in your reading.
What does repeatavke results mean?
Results are repeatable if you can repeat an experiment multiple times and get the same results.
WHat does reproduclible results mean?
Results are reproduclible if someone else can recreate your experiment using different experiment or methods and get same results you do.
What do valid results mean?
Valid results arises from a suitable procedure to answer the original questions. If you don’t keep all vairiables constant apart from the ones your testing you haven’t only tested the variable you are investigating and so the results are not valid.
What are the accurate results?
An accurate result is really close to the true answer. You can only comment on how accurate a result is if you already know the true value.
