prep for the ISA and General physics Flashcards
When recording results in a table, how many significant figures do you give it to?
Give it to the no. of significant levels of the instruments.
Give any means calculated to the same no. of significance levels.
If you process data which are given to different numbers of significant figures, how many do you use in the answer?
The no. of significant figures used in the value with the smallest amount.
How can random errors be reduced?
Taking repeat readings.
What is systematic error?
Errors that show a trend, bias or pattern. It deviates from the true reading by a fixed amount each time.
How is the uncertainty in a set of values found?
There are 3 options.
Random error. Uncertainty=(±range÷2) units.
Precision of instrument. Uncertainty=± smallest units on the scale.
Judgment. Like having kinks in a wire. Uncertainty=±(3 X precision of the instrument.)
Pick the largest.
Always have units.
If we have to combine the errors from different measurements and they have different units, what do we do?
Find % uncertainty.
(Uncertainty ÷ mean value.) X 100.
Never give to more than 2 sig figs.
How do you combine % uncertainties ?
They add up if you X, +, - or ÷
If a value is squared, multiply it by 2.
If a value is square rooted, divide by 2.
How would you find the percentage of something?
How would you find 1.3% of 9.42?
(9.42÷100) X 1.3
What is an accurate measurement?
An accurate measurement is one where independent measurements cluster about the true
value of the measured quantity.
What is a precise measurement?
A precise measurement is one where independent measurements of the same quantity
closely cluster about a single value that may or may not be the correct value.
Does systematic errors affect precision or accuracy?
Only the accuracy.
When drawing a table, what should each column heading have?
A quantity and a unit. The units should be give in brackets.
How big should the graph be?
Big enough so that the plotted points take up at least half the page.
When drawing a graph, when should the axis start ?
At the origin. Both should start at 0.
When drawing a graph, what divisions in the axis aren’t allowed?
3, 6, 7, 9 and others like that.
Should the line of best fir go through the origin?
Only if it fits the data. Don’t force it through.
What are the units used for the gradient?
There aren’t any.
How do you know if a set of results are reliable?
The repeat values are similar to each other and they area close to the line of best fit.
What are control variables?
variables that you couldn’t have changed, like equipment you were given.
How can reliability be improved?
Take repeat readings.
How can valibilty be improved?
A larger range and more repeat values.
Why might some results not be reliable?
not reliable because (some of) the points are not
very close to the line of best fi
What will you have to do in the isa?
Calculate percentage uncertainties.
Design your own experiment.
Efficiency volatge÷emf
You will have to use power equations.
Why is it important to test by experiment the prediction of scientific theory?
As if a reliable experiment doesn’t support the hypothesis, the hypothesis must be changed.
