Flashcards in prep for the ISA and General physics Deck (24)

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1

## 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.

2

## 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.

3

## How can random errors be reduced?

### Taking repeat readings.

4

## What is systematic error?

### Errors that show a trend, bias or pattern. It deviates from the true reading by a fixed amount each time.

5

## 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.

6

## 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.

7

## 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.

8

##
How would you find the percentage of something?

How would you find 1.3% of 9.42?

### (9.42÷100) X 1.3

9

## What is an accurate measurement?

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An accurate measurement is one where independent measurements cluster about the true

value of the measured quantity.

10

## 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.

11

## Does systematic errors affect precision or accuracy?

### Only the accuracy.

12

## When drawing a table, what should each column heading have?

### A quantity and a unit. The units should be give in brackets.

13

## How big should the graph be?

### Big enough so that the plotted points take up at least half the page.

14

## When drawing a graph, when should the axis start ?

### At the origin. Both should start at 0.

15

## When drawing a graph, what divisions in the axis aren't allowed?

### 3, 6, 7, 9 and others like that.

16

## Should the line of best fir go through the origin?

### Only if it fits the data. Don't force it through.

17

## What are the units used for the gradient?

### There aren't any.

18

## 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.

19

## What are control variables?

### variables that you couldn't have changed, like equipment you were given.

20

## How can reliability be improved?

### Take repeat readings.

21

## How can valibilty be improved?

### A larger range and more repeat values.

22

## Why might some results not be reliable?

###
not reliable because (some of) the points are not

very close to the line of best fi

23

## 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.

24