Uncertainties

Question 1

Why must we take in to consideration uncertainties?

Answer 1

We must realise a degree of uncertainty associated with measuring a physical county.

Question 2

Systematic effects

Answer 2

These can occur when the measurements are affected in the same way for example a meter stick may have “shrunk” thus giving consistently incorrect results.
At our current level systematic effects tend to be small enough to ignore.
When accuracy is of the utmost importance, the apparatus will be calibrated against a known standard.

Question 3

Random uncertainties

Answer 3

Random fluctuations can affect measurements from reading to reading, e.g. consecutive timings of the period of a pendulum can differ. The best estimate of the true value is given by repeating the readings and then calculating the mean value.

Question 4

Random uncertainty formula

Answer 4

Max reading - minimum reading divided by number of readings.

Question 5

Scale reading uncertainty

Answer 5

This value indicates how well an instrument scale can be read.
An estimate of reading uncertainty for an analogue scale is generally taken as:
± half the least division of the scale.
For a digital scale it is taken as
± 1 in the least significant digit displayed.

Question 6

Comparison of uncertainties

Answer 6

When comparing uncertainties, it is important to take the percentage in each. Suppose in an experiment the following uncertainties were found.
The overall uncertainty should be taken as the highest percentage uncertainty.
In this case, this would be the reading uncertainty at 2 %.

Question 7

Systematic error description

Answer 7

A permanent deflection in the same direction of a true value