Measurements Flashcards
Physical quantity
A term that is used to include numerically measurable features
of many different items. It has a numerical magnitude and a
unit.
Base quantities
The seven physical quantities of the SI system by which all other physical quantities are defined.
They are: mass, length, time, temperature, amount of
substance, electric current and luminous intensity.
Base units
The seven units of the SI system, related to the base quantities, whose magnitude is defined without referring to other units. (the case for base quantities)
They are: kg, m, s, K, mol, A and cd.
Derived quantities
Physical quantities that are derived from base quantities and can be expressed in terms of products and quotients of base quantities.
Dimensionless quantity
A quantity without an associated physical dimension, it is thus a pure number.
Homogenous equation
An equation where the base units of all the terms are the same.
Experimental errors
Uncertainties in measured quantities that arise from different sources due to the limitations of the observer, the measuring instrument used, and the method used.
Random errors
Random errors are present when the measured values produce errors of different magnitudes and signs. These readings are scattered about the mean value with no fixed pattern.
Systematic errors
Systematic errors are present when the measured values produce errors of the same magnitude and sign.
Precision
Precision is determined by the range of values/measurements. The smaller the range, the more precise.
Accuracy
Accuracy is determined by the closeness of the value/measurement to the true value of the quantity being measured.
Uncertainty
The range of values on both sides of a measurement in which the actual value of the measurement is expected to lie.
Absolute uncertainty
The actual numerical uncertainty
Fractional uncertainty
The ratio of absolute uncertainty to the measured value of a quantity.
Vector
A quantity having both magnitude and direction.
