Edexcel A-Level Physics 9PH0
Working as a Physicist
Mechanics
Electric Circuits
Materials
Waves and Particle Nature of Light
Further Mechanics
Electric and Magnetic Fields
Nuclear and Particle Physics
Thermodynamics
Space
Nuclear Radiation
Gravitational Fields
Oscillations
Working as a Physicist
Uncertainty and how uncertainties combine
- 2 things to know
- Papers 1, 2 and 3
Overview
Recall questions on estimating uncertainty from an analogue scale, a digital meter and repeated readings, and on adding absolute or percentage uncertainties.
What you need to know
Answer each one before you reveal it.
How are uncertainties combined when quantities are added, multiplied, or raised to a power?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What does the uncertainty in a measurement tell you?
Model answer
It gives the interval either side of the reading within which the true value is expected to lie.
- 2
How is the uncertainty in a single reading taken from an analogue scale usually estimated?
Model answer
It is taken as half the smallest scale division.
- 3
How is the uncertainty in a reading from a digital meter usually taken?
Model answer
It is taken as plus or minus the last displayed digit, which is the resolution of the instrument.
- 4
How is the uncertainty found from a set of repeated readings?
Model answer
It is taken as half the range, that is half the difference between the largest and the smallest value.
- 5
How are uncertainties combined when two quantities are added or subtracted?
Model answer
Their absolute uncertainties are added.
- 6
How are uncertainties combined when two quantities are multiplied or divided?
Model answer
Their percentage uncertainties are added.
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