3.1 Measurements and their Errors

Question 1

What are the 7 SI units? What are they for?

Answer 1

Metre (length), second (time), kilogram (mass), ampere (electric current), kelvin (temperature), mole (substance amount)

Question 2

Conversion from eV to J

Answer 2

x 1.6 x10^-19

Question 3

Value of all the (big) prefixes

Answer 3

T x10^12
G x10^9
M x10^6
k x10^3

Question 4

Value of all the (small) prefixes

Answer 4

c x10^-2
m x10^-3
micro x10^-6
n x10^-9
px10^-12
f x10^-15

Question 5

Conversion from kWh to J

Answer 5

x3.6x10^6

Question 6

How to reduce random errors?

Answer 6

By repeating steps and creating a mean (ignoring anomalies)

Question 7

What is a systematic error?

Answer 7

Difference from true value but by the same amount each time

Question 8

How to reduce systematic error?

Answer 8

Change method/ person doing experiment, use better instruments, be more careful in general

Question 9

What is the difference between readings and measuremnts?

Answer 9

Readings have only one judgement, whereas measurements have two.

Question 10

How do you find out the absolute uncertainty of something?

Answer 10

Look at the upper and lower limits of the mean value.
Half of the measuring instrument’s smallest scale division.

Question 11

How do you find the percentage uncertainty of something?

Answer 11

(absolute uncert./measured value) x100

Question 12

How do you find the fractional uncertainty of something?

Answer 12

absolute uncert./measured value

Question 13

How do you combine uncertainties when multiplying quantities?

Answer 13

add them together