Experimental Design (OCR A Level Physics): Flashcards
Exam code: H556
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Define preliminary research.
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Cards in this collection (38)
Define preliminary research.
Preliminary research is researching similar studies or experiments before designing an investigation, to help pose a hypothesis, choose suitable apparatus and techniques and identify the variables to control.
What is the purpose of carrying out preliminary studies after preliminary research?
To identify additional variables that affect the experiment and to find the best way to control them.
Define accuracy.
Accuracy is how close a reading or measurement is to its true value.
Define precision.
Precision is how similar repeat readings or measurements are to each other.
Accuracy is affected by .......... errors, whereas precision is affected by .......... errors.
Accuracy is affected by systematic errors, whereas precision is affected by random errors.
True or False?
A set of precise measurements must also be accurate.
False.
Precision describes how tightly repeat readings cluster together, which is independent of accuracy. Readings can be precise but not accurate if a systematic error shifts them all away from the true value.
What is a limitation in an experiment?
A limitation is a design flaw or fault that affects the accuracy of the experiment and should be identified and corrected to make the results valid.
What is an independent variable?
The independent variable is the only variable that is changed throughout an experiment.
What is a dependent variable?
The dependent variable is the variable that is measured to determine the outcome (the results) of an experiment.
What is a control variable?
A control variable is any other variable that may affect the results and must be kept constant (controlled or monitored) so the results stay valid.
Why is it essential to keep control variables constant?
If control variables are not kept constant they could affect the results, making them unreliable and the experiment invalid.
When investigating Charles' law, temperature is the .......... variable and volume is the .......... variable.
When investigating Charles' law, temperature is the independent variable and volume is the dependent variable.
True or False?
When investigating Boyle's law, temperature is the independent variable.
False.
For Boyle's law the pressure is varied (independent variable), while the temperature and number of moles are kept constant (control variables).
Define a random error.
A random error causes unpredictable fluctuations in an instrument's readings, due to uncontrollable factors such as changes in environmental conditions.
Define a systematic error.
A systematic error arises from a faulty instrument or a flaw in the method and is repeated consistently every time the measurement is taken.
How can random errors be reduced?
Repeat the measurements several times and calculate an average (mean).
How can systematic errors be reduced?
Recalibrate the instrument or use a different one, and make corrections or adjustments to the technique.
Define a zero error.
A zero error is a systematic error that occurs when an instrument gives a non-zero reading when the true reading is zero.
Define the resolution of a measuring instrument.
Resolution is the smallest change in the quantity being measured that gives a perceptible change in the instrument's reading.
.......... errors affect the precision of measurements, whereas .......... errors affect the accuracy.
Random errors affect the precision of measurements, whereas systematic errors affect the accuracy.
True or False?
Repeating measurements and averaging them reduces systematic error.
False.
Repeating and averaging reduces random error. Systematic errors are reduced by recalibrating the instrument or correcting the method — averaging does not remove them.
Name three skills that demonstrate proficiency in practical work.
Any three of:
using a range of apparatus and instruments, including ICT such as a datalogger
using instruments with confidence and reasonable accuracy
carrying out the steps of a practical in the correct order
recording readings while still observing the apparatus
fine-tuning the apparatus or technique to obtain a suitable range of readings
Give an example of ICT that could be used to collect data in an experiment.
A datalogger, an app or a computer.
Why might you "fine-tune" the apparatus or technique during an investigation?
To obtain a suitable range of readings.
A variable such as .......... should be measured before and after readings are taken, to check whether it has changed during the experiment.
A variable such as room temperature should be measured before and after readings are taken, to check whether it has changed during the experiment.
True or False?
Readings should only be recorded after you have finished observing the apparatus.
False.
A key practical skill is recording readings while still observing the apparatus, so that changes can be noticed as they happen.
Define the resolution of a measuring instrument.
Resolution is the smallest change in the physical quantity being measured that results in a change in the reading given by the instrument.
True or False?
A mercury thermometer reading to 1 °C has a higher resolution than a digital thermometer reading to 0.1 °C.
False.
The digital thermometer can detect a smaller change (0.1 °C), so it has the higher resolution.
Which instrument is most suitable for measuring the diameter of a thin wire, and why?
A micrometer screw gauge (or vernier callipers), because it has the highest resolution for small measurements.
Why is a metre ruler, rather than vernier callipers, used to measure the original length of a wire?
The wire has a moderate length that is too long to be measured with a vernier scale.
What is a travelling microscope used to measure in a Young modulus experiment?
Small changes in length, such as the extension of the wire.
To determine the Young modulus of a wire, you must measure its diameter, original length, extension and the .......... applied to the wire.
To determine the Young modulus of a wire, you must measure its diameter, original length, extension and the weight applied to the wire.
State the SI base unit and symbol for mass and for temperature.
Mass: kilogram (kg)
Temperature: kelvin (K)
A volume of 1 cm3 is equivalent to one .........., and 1 dm3 is equivalent to one ...........
A volume of 1 cm3 is equivalent to one millilitre (ml), and 1 dm3 is equivalent to one litre (l).
How many cubic centimetres (cm3) are there in 1 m3?
There are 106 cm3 (1 000 000 cm3) in 1 m3.
Why is it important to use the correct symbol alongside a unit of measurement?
So the quantity is unambiguous — for example, m3 specifically denotes cubic metres.
True or False?
One litre is equal to one cubic metre.
False.
One litre is equal to 1 dm3 = 0.001 m3; one cubic metre contains 1000 litres.
What is 1 tonne expressed in kilograms?
1 tonne = 1000 kg.
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