2. SCALAR
QUANTITIES
Physical quantities that have magnitude
only.
Example:
length, time, temperature, mass, speed, ar
ea, volume and density.

3. VECTOR
QUANTITIES
Physical quantities that have magnitude
and direction
Example:
displacement, momentum, acceleration, vel
ocity and force.

5. • The ability of the instrument to
Precision measure a quantity with little or no
deviation among measurements.
• How close the measurement made
Accuracy is to the actual value.
• Ability of instrument to detect
Sensitivity change.

6. RANDOM
ERRORS
ERROR IN
MEASUREMENT
SYSTEMATICS
ERRORS

7. • 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.

8. ERROR IN MEASUREMENT
RANDOM SYSTEMATIC
ERRORS ERRORS
PARALLAX
ZERO ERRORS
ERRORS

9. Error
Error is the difference between the actual value of a quantity and the
value obtained in measurement.
There are 2 main types of error
- Systematic Error
- Random Error
Systematic Error
Systematic errors are errors which tend to shift all measurements in a
systematic way so their mean value is displaced. Systematic errors can
be compensated if the errors are known.
Examples of systematic errors are
zero 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.

10. Zero error
1. A zero error arises when the measuring instrument does not
start from exactly zero.
2. Zero errors are consistently present in every reading of a
measurement.
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.)

11. NEGATIVE ZERO ERROR: The pointer of the ammeter does not place on
zero but a negative value when no current flow through it.)
(POSITIVE ZERO ERROR: The pointer of the ammeter does not place
on zero but a negative value when no current flow through it.)

12. Random errors
1. Random errors arise from unknown and unpredictable variations
in condition.
2. It fluctuates from one measurement to the next.
3. Random errors are caused by factors that are beyond the
control 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.

13. Parallax error
A parallax error is an error in reading an instrument due to the eye
of the observer and pointer are not in a line perpendicular to the
plane of the scale.

14. Precision
1. Precision is the ability of an instrument in
measuring a quantity in a consistent manner with
only a small relative deviation between readings.
2. The precision of a reading can be indicated by its
relative deviation.
3. The relative deviation is the percentage of mean
deviation for a set of measurements and it is defined
by the following formula:

15. Accuracy
1. The accuracy of a measurement is the
approximation of the measurement to the actual
value for a certain quantity of Physics.
2. The measurement is more accurate if its number
of significant figures increases.
3. Table above shows that the micrometer screw
gauge is more accurate than the other measuring
instruments.

16. 4. The accuracy of a measurement can be increased by
•taking a number of repeat readings to calculate the mean value of
the 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 replace
a ruler.
5. The difference between precision and accuracy can be shown by
the spread of shooting of a target (as shown in Diagram below).

17. Sensitivity
1. The sensitivity of an instrument is its ability to detect small
changes in the quantity that is being measured.
2. Thus, a sensitive instrument can quickly detect a small
change in measurement.
3. Measuring instruments that have smaller scale parts are
more sensitive.
4. Sensitive instruments need not necessarily be accurate.