Practical Skills

Question 1

Name the six S.I base units?

Ignore the candela- for brightness/intensity

Answer 1

K - kelvin
mol - mole
kg - mass
m - metre
s - second
A - ampere

Question 2

What is meant by the term accurate?

Answer 2

How close a result is to the true value.

Question 3

What is meant by the term precise?

Answer 3

How closely the repeated results are to one another.

Question 4

What are errors?

Answer 4

The difference between an individual result and the true value.

Question 5

What is an uncertainty?

Answer 5

An estimate of the range of values within which the true values lies for a measurement.

Question 6

What is the absolute uncertainty?

Answer 6

The uncertainty in the quantity (e.g. distance) being measured.

(This is often the resolution of the instrument etc for a vernier calliper +/- 0.01mm)

Question 7

How can the percentage uncertainty of a single measurement be calculated?

Answer 7

Percentage uncertainty = (Absolute uncertainty / measured value) x 10

Note: using a measurement with a higher resolution (smaller absolute uncertainty) will decrease the percentage uncertainty.

Question 8

How can the percentage uncertainty for multiple measurements be calculated?

Answer 8

Percentage uncertainty (multiple readings) = (half the range / mean value) x 100