Errors and Uncertainities Flashcards
Define systematic errors.
Systematic errors are uncertainties in the measurement of the physical quantities due to faults in instruments, surrounding conditions or errors made by the observer.
The characteristic of the systematic error is that the size of the error is roughly constant and the reading may be greater or less than the actual value.
What can systematic errors be removed by?
Systematic errors cannot be reduced by repeating the values and taking an average.
It can only be removed by improving experimental techniques.
1) Change the instrument or check for Zero error.
2) Take the reading of a known value.
3) Change the observer and he uses his own instrument for measurement.
Give example of sources of error:
Zero error: In Vernier Callipers, Micrometre screw gauge or stop watches.
Personal Error Or Physical Constraints or limitations such as reaction time or height etc.
Wrong Assumptions: Value of g= 9.81 or 10m/s^2
Errors due to instrument: Wrong Calibration of instruments.
Define random errors.
Random errors are uncertainties or mistakes in a measurement made by the observer taking the measurement.
The characteristic of random errors is that it can be greater or less than an actual value and the magnitude of the error is not constant.
What can random errors be reduced by?
Random errors cannot be removed however they can be reduced.
It can be reduced by repeating the reading and averaging or plotting the graph of best-fit line.
What are the sources of random errors?
Errors due to parallax error: Taking readings wrong positioning of the eyes.
Timing oscillations without fiducial mark: Readings may always be made at the same point.
Applying different pressures while closing the gap of the micrometre and Vernier callipers.
Sudden changes in temperature or wind effect during an instrument.
What is the definition of precision?
Precision refers to how close a set of values are to each other.
It is given by the deviation of a reading x from mean/actual value x̄, calculated as d= ( x̄-x). Precision is determined by deviation irrespective of the sign.
smaller the value greater the precision.
A measurement can be precise but it may not be correct.
Define accuracy
Accuracy refers to the closeness of a measured value to the “actual”, “known” or “true value”.
Accuracy is measured by calculating the percentage error i.e. smaller the percentage error the greater the accuracy.
Are precise readings always accurate?
Precise readings may not be accurate as they deviate from the actual value but an accurate value is correct as it is close to the actual value.
Which type of error effect accuracy?
Systematic error effects accuracy.
Which type of error effects precision?
Random errors effect precision.
Define scalar quantities.
A quantity which can be described fully by giving its magnitude and unit is known as scalar quantity.
Define vector quantities.
A vector quantity has a magnitude, unit and direction.
Give examples of vector quantities.
Displacement, velocity, force, momentum, electrical field strength, acceleration, weight and torque.
Give examples of scalar quantities.
Length, mass, time, speed, energy, power, temperature, pressure and electrical current.
