how can you approximate uncertainty from a graph?
plot error bars, find the steepest or shallowest gradients, find the difference in gradient with the line of best fit
how to calculate percentage uncertainty
uncertainty/actual value x100
what is precision
how close repeated measurements are to each other
what is accuracy
how close a measured value is to an actual value
what is resolution
the smallest detectable change in input e.g. 1mm on a cm ruler
what is sensitivity
the ratio of output to input e.g. the change in p.d. across a thermistor when the temperature changes by 1°C
what is stability/repeatability
the extent to which repeated measurements will give the same result (same method)
what is reproducibility
the extent to which measurements will give the same result using a different method
what is response time
the time interval between a change in input and the corresponding change in output
what is a zero error
the output given for zero input
what is noise
variations (which may be random) superimposed on a signal
what is calibration
determining the relation between output and true input value
how to determine uncertainty of an instrument (4 ways)
use the resolution, measure the stability of the instrument, compare with another instrument, use the range/spread (range/2) of repeated measurements
use percentage uncertainties
how to find uncertainty when adding or subtracting values
add the absolute uncertainties of each value
how to find uncertainty when multiplying or dividing values
add the percentage uncertainties of each value
how to find the uncertainty when raising a quantity by a power
multiply the percentage uncertainty by the number of the power
what is systematic error
an error which causes all readings to differ from the true value by a fixed amount (fix using different method/apparatus), can arise from lack of calibration
what is a random error
unpredictable variation between measurements that leads to a spread of values around a true value (can be minimised by taking more measurements)
what is a hazard
an event which has the potential to cause harm
what is a risk
the likelihood of a hazard arising to cause harm
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1. imaging1
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2. signalling0
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3. sensing0
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4+5 materials10
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6. waves0
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7. quantum0
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8+9. forces and motion0
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10. radioactive decay and capacitor discharge0
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11. SHM0
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12. out into space0
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13. our place in the universe0
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14. simple models of matter0
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15. boltzmann factor0
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16. electromagnetic machines0
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17. charge and field0
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18+19. probing and ionising0
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Practical Skills20
