SCALAR QUANTITIES Physical quantities that have magnitude only. Example:length, time, temperature, mass, speed, ar ea, volume and density.
VECTOR QUANTITIES Physical quantities that have magnitude and direction Example:displacement, momentum, acceleration, vel ocity and force.
• The ability of the instrument toPrecision measure a quantity with little or no deviation among measurements. • How close the measurement madeAccuracy is to the actual value. • Ability of instrument to detectSensitivity change.
RANDOM ERRORS ERROR IN MEASUREMENTSYSTEMATICS ERRORS
• Due to the calibration of instrument.SYSTEMATIC • Zero error- due to non-zero reading when actual reading should ERROR be zero. • Due to mistakes made when making measurement either through incorrect positioning of RANDOM eye or instrument. • May also occur when there is a ERROR sudden change of environmental factors like temperature , air circulation or lighting.
ERROR IN MEASUREMENT RANDOM SYSTEMATIC ERRORS ERRORS PARALLAX ZERO ERRORS ERRORS
ErrorError is the difference between the actual value of a quantity and thevalue obtained in measurement.There are 2 main types of error- Systematic Error- Random ErrorSystematic ErrorSystematic errors are errors which tend to shift all measurements in asystematic way so their mean value is displaced. Systematic errors canbe compensated if the errors are known.Examples of systematic errors arezero error, which cause by an incorrect position of the zero point,an incorrect calibration of the measuring instrument. consistently improper use of equipment.Systematic error can be reduced by Conducting the experiment with care. Repeating the experiment by using different instruments.
Zero error1. A zero error arises when the measuring instrument does notstart from exactly zero.2. Zero errors are consistently present in every reading of ameasurement.3. The zero error can be positive or negative. NO ZERO ERROR: The pointer of the ammeter place on zero when no current flow through it.)
NEGATIVE ZERO ERROR: The pointer of the ammeter does not place onzero but a negative value when no current flow through it.)(POSITIVE ZERO ERROR: The pointer of the ammeter does not placeon zero but a negative value when no current flow through it.)
Random errors1. Random errors arise from unknown and unpredictable variationsin condition.2. It fluctuates from one measurement to the next.3. Random errors are caused by factors that are beyond thecontrol of the observers.4. Random error can cause by personal errors such as human limitations of sight and touch. lack of sensitivity of the instrument: the instrument fail to respond to the small change. natural errors such as changes in temperature or wind, while the experiment is in progress. wrong technique of measurement.5. One example of random error is the parallax error.Random error can be reduced by- taking repeat readings- find the average value of the reading.
Parallax errorA parallax error is an error in reading an instrument due to the eyeof the observer and pointer are not in a line perpendicular to theplane of the scale.
Precision1. Precision is the ability of an instrument inmeasuring a quantity in a consistent manner withonly a small relative deviation between readings.2. The precision of a reading can be indicated by itsrelative deviation.3. The relative deviation is the percentage of meandeviation for a set of measurements and it is definedby the following formula:
Accuracy1. The accuracy of a measurement is theapproximation of the measurement to the actualvalue for a certain quantity of Physics.2. The measurement is more accurate if its numberof significant figures increases.3. Table above shows that the micrometer screwgauge is more accurate than the other measuringinstruments.
4. The accuracy of a measurement can be increased by•taking a number of repeat readings to calculate the mean value ofthe reading.•avoiding the end errors or zero errors.•taking into account the zero and parallax errors.•using more sensitive equipment such as a vernier caliper to replacea ruler.5. The difference between precision and accuracy can be shown bythe spread of shooting of a target (as shown in Diagram below).
Sensitivity1. The sensitivity of an instrument is its ability to detect smallchanges in the quantity that is being measured.2. Thus, a sensitive instrument can quickly detect a smallchange in measurement.3. Measuring instruments that have smaller scale parts aremore sensitive.4. Sensitive instruments need not necessarily be accurate.