Working as a physicist Flashcards
What is an accurate result?
One which is close to the true value
What is a precise result for repeated data?
One where the range that the repeated data is spread over is small
What are repeatable results?
If the experiment was repeated by the same experimenter using the same method and equipment then the same results would be obtained
What are valid measurements and what can reduce validity of results?
The measurements measure what they are supposed to be measuring. Not controlling all control variables reduces validity because you won’t be testing the effect of the independent variable alone.
What are reproducible results?
If the experiment was repeated by a different experimenter using a different method and different equipment then the same results would be obtained
Why is reproducibility a better test of quality than repeatability in terms of systematic error?
Because its less likely that the same systematic errors could affect both methods
What is a fair test?
One in which only the independent variable has been allowed to affect the dependent variable
What is the resolution of an instrument?
The fineness to which an instrument can be read
What is meant by an error?
The difference between your measured value and the true value of whatever you re measuring
What is meant by a systematic error?
Errors which are the same every time you repeat the experiment. Readings differ from the true value by a constant amount each time a measurement is made
What are 3 potential causes of systematic error?
Environment, methods of observation or instruments used
Why are systematic errors hard to spot?
Because they are the same each time
Do systematic errors affect accuracy, precision or both?
Affect accuracy but not precision
What are 2 ways to reduce systematic errors and how can you correct your results?
Check apparatus at the start of the experiment and conduct the experiment carefully keeping an eye on the environment. Repeat the experiment using a different method or different equipment or compare results with others. Find the value of the systematic error and use it to correct your results.
What is meant by a random error and how results vary from measurement to measurement?
One which causes readings to be spread bout the true value: error not the same each time. Results vary in an unpredictable way from measurement to measurement.
What are 2 ways to reduce random error in individual measurements and 1 way to reduce random error in calculated results like the mean?
Keep controlled variables exactly the same throughout the experiment. Use apparatus with a better resolution. Do more repeats.
Does random error affect accuracy, precision or both and how does this make them easier to spot?
It affects precision and accuracy so is easy to spot because precision leads to a large range of readings.
Can random error be corrected?
No because they are not the same each time and are not predictable
What is meant by zero error and what kind of error does this lead to?
Instrument doesn’t measure zero when the quantity it is measuring is zero. This leads to systematic error
What is an anomaly?
A value which is judged to not be part of variation caused by random error/ uncertainty
What is meant by the margin of error?
The maximum difference between your value and the true value
What is percentage uncertainty and how do we reduce it?
The uncertainty given as a percentage of the measurement. Reduce it by measuring larger values.
What are the 7 base quantities and their units?
Mass(kg) Length (m) Time (s) Current (A) Temperature (K) Amount of substance (mol) Luminous denisty (cd)
Name three factors which can influence decisions about science.
Economic factors
Social factors
Environmental factors
State how many significant figures calculated values must be given to.
Same number of sig figs as the data value with the fewest sig figs in your calculation
If you plot a linear graph, how can you tell your independent and dependent are directly proportional?
Graph will be a straight line through the origin.
