Practical Skills

Question 1

Base Quantities

Answer 1

Mass
Distance
Time
Electric Current
Temperature
Amount of Substance
Luminous Intensity

Question 2

Base Units/ Symbols

Answer 2

Kilogram (kg)
Metre (m)
Second (s)
Ampere (A)
Kelvin (K)
Mole (mol)
Candela (cd)

Question 3

Prefixes, Symbols and Multipliers

Answer 3

femto f -15
pico p -12
nano n -9
micro μ -6
milli m -3
centi c -2
kilo k 3
mega M 6
giga G 9
tera T 12
peta P 15

Question 4

Order of Operations

Answer 4

Brackets
Indices
Division
Multiplication
Addition
Subtraction

Question 5

Measurement Error

Answer 5

The difference between the true value and the measured value.
The true value is taken from the data book or given by the manufacturer

Question 6

Random Error

Answer 6

A measurement error in which measurements vary unpredictably.
For Example: Parallax Error
Calculate Mean to reduce random error

Question 7

Systematic Error

Answer 7

Where values vary from the true values by the same amount each time.
For Example: Zero Error

Question 8

Absolute Uncertainty

Answer 8

The spread of values within which are true

Question 9

Percentage Uncertainty

Answer 9

100 x (Absolute Uncertainty/ Measured Value)

Question 10

Combining Uncertainties

Answer 10

Uncertainties always increase
They never cancel out or subtract
1) When quantities (with the same units) are added or subtracted, the absolute uncertainties are added
2) When quantities (any units) are multiplied or divided, the percentage uncertainties are added
3) When quantities are raised to the power n, the percentage uncertainty is multiplied by n

Question 11

Other Methods of Calculating Uncertainty

Answer 11

1) Calculate the Maximum (or minimum) calculated value. The difference between this and the actual value is absolute uncertainty.
2) Draw lines of best and worst fit using error bars. Calculate their gradients
Uncertainty on gradient = Gradient from best fit line - Worst fit line

Question 12

Accuracy

Answer 12

An experiment produces a result close to the accepted value

Question 13

Precision

Answer 13

The spread of repeated results in the same experiment

Question 14

Reliability

Answer 14

Consistent results across different experiments

Question 15

Resolution

Answer 15

Smallest division on the measuring instrument

Question 16

Percentage Difference

Answer 16

100 x (Measured Value - True Value) / True Value

Question 17

Determine Accuracy

Answer 17

If % difference < % uncertainty, then the experiment is considered accurate