Working As A Physicist

Independent Variable

The variable that is changed or controlled in a scientific experiment

Dependent variable

A dependent variable is the variable being tested and measured in a scientific experiment.

Precision

Refers to the consistency of results from repeated measurements

Accuracy

How close a measured value is to the true or accepted value

Error

Difference between a measured value and the true value

Uncertainty

The interval within which the true value of a measurement is expected to lie

How do you work out percentage uncertainty?

Percentage uncertainty = (absolute uncertainty / measurement taken) x 100

How do you find an uncertainty of a mean?

Range/2

Uncertainty of a DIGITAL reading?

resolution

How do you add absolute uncertainties of the same type of measurement?

Add the uncertainties

How do you add absolute uncertainties of different measurements?

Convert to percentage uncertainties and add them

If a value with known uncertainty is squared, how do you find the uncertainty of the squared value?

2x the percentage uncertainty

If you add or take away terms, the absolute uncertainty of the new value is...

The sum of the absolute uncertainties of the terms

If you multiply or divide terms, the percentage uncertainty of the new value is...

The sum of the percentage uncertainties of the terms

If you raise a term to a power, it's percentage uncertainty is...

Whatever it was raised to the power by, multiplied by the percentage uncertainty, then take the modulus

When can you not add percentage uncertainties?

When there is no multiplication or division

Uncertainty of a measurement (e.g thermometer/analogue)

Half resolution

Example of Systematic Errors

Zero, Parallax

To reduce: recalibrate

Example of Random Errors

Electronic Noise in a circuit

To reduce: repeat & mean