The seven quantities of base are length, mass, Time, electric current, temperature, intensity of light and amount of substance.
These objects are exposed in terms of their measurable features known as physical quantities such as length, breath, thickness, mass, volume, density, time, temperature etc.
Use of St measurements helps all scientists to share and compare their observations and results easily.
The international committee on weights and measures in 1961 recommended the use of a system consisted of seven base units known as international system of units abbreviated as Sl.
i. 5000 mm = 5000 1000 m=5m ii. 5000 cm = 50000 100 m = 500m lii. 3000 g = 3000 1000 kg=3kg Ιν. 2000μς 2000×10-6s-2×10-3
To write numbers using scientific notation, move the decimal point until only one non-zero digit remains on the left. Then count the number of places through which the decimal point is moved and use this number as the power or exponents of 10.
Metre rule, measuring tape.
The smallest measurement that can be taken with a metre rule is Imm. one millimeter is known as least count of the metre rule.
If the metre rule is read from an angle, the object will appear to be of the different length. This is known as parallax error.
It is an instrument used to measure small lengths down to 1/10th of a millimeter. It can be used to measure the thickness, diameter, width and depth of an object.
Least count of Veriner Callipers is the difference between one main scale division (M.S) and one Vernier scale (V.S) division. Hence, Least count = 1 M.S. div - I V.S. div. Imm-0.9mm = 0.1mm
The instrument screw gauge is more precise than Vernier Calliper because the least count of vernier is 0.01cm while the least count of screw gauge is 0.001cm.
The minimum length which can be measured from screw gauge is called least count of screw gauge. Least count of screw gauge can be found by.
If the zero of the main scale does not coincide with the zero of the vernier scale, when the jaws closed there is zero error in the instrument.
To remove the error in the instrument is called zero correction.
A physical balance is used to measure mass. In our daily life. We use the term weight instead of mass.
While using, a knob present on the top of the device is pressed. This result in the starting of the watch. The same knob is again pushed to stop it. After noting the reading, the same knob is again pressed to bring back the needles to the zero position. Now-a-days, electronic/digital watches are also available which can measure one hundredth part of a second.
It is a cylinder made of glass or transparent plastic with a scale divided in cubic centimeter (cm³ or CC) or millilitres (mL) marked on it.
It is used to find the volume of liquids and non-dissolvable solids.
They occur due to personal performance. The limitation of the human perception such as the inability to perfectly estimate the position of the pointer on a scale.
Human error can be reduced by ensuring proper training, techniques and procedure to handle the instruments and avoiding environmental distraction or disturbance for proper focusing. The best way is to use automated or digital instruments to reduce the impact of human errors.
They refer to an effect that influence all measurements of particular measurements equally. It produces a consistence difference in reading. It occurs to some definite rules.
It may occur due to zero error of instrument, poor calibration of instrument or incorrect marking. The effect of this kind of error can be reduced by comparing the instrument with another which is known to be more accurate. Thus a correction factor can be applied.
These errors occur when repeated measurements of a quantity give different values Infinis Hofer conditions. It is due to some unknown causes which are unpredictable.
For Example: changes in temperature, pressure, humidity, voltage, etc.
The effect of random errors can be reduced using several or multiple readings and then taking their average or mean value. Similarly, for the measuring time period of oscillating pendulum, the time of several oscillation, say 30 oscillations is noted and then mean or average value of one oscillation is determined.
In any measurement, the accurately known digits and the first doubtful digit are known-as significant figures.
Precesion refers to the consistency or repeatability of measurement.
Accuracy refers to how close a measurement is to the true or accepted value.
(i) Use well calibirated instruments.
(ii) Take multiple readings and find the average.
(iii) Avoid parallax errors by aligning the eye properly with scale.
(iv) Ensure environmental conditions are stable.
(i) Place the wire between the anvil and spindle of the screw gauge.
(ii) Turn the thimble until the wire is held firmly.
(iii) Record the main scale and circular readings.
(iv) Use the formula.
Diameter = Main Scale Reading + [circular scale reading least count].
Least count of Vernier Caliper: 0.01, cm.
Least count of Screw Gauge: 0.001, cm.
Importance: It determines the smallest measurement of an instrument can make ensuing higher accuracy.
Dimensional analysis uses dimensions [e.g., (L) for length] to check to correctness of physical equations and convert units.
Systematic Errors: Consistent errors caused by faulty equipment or incorre methods.
Example: A miscalibirated scale always showing 2 kg extra.
Example: Fluctuations in stopwatch readings.
Random Errors: Unpredictable errors due to environmental factors or human
Significant figures indicate the precesion of a measurement.
Rules:
(i) Non-zero digits are significant.
(ii) Zeros between non-zero digits are significant.
(iii) Leading zeros are not significant.
(iv) Trailing zeros in a decimal are significant.
Example: 0.00450 has 3 significant figures.
Scientific notation simplifies working with very large or small numbers by expressing them in the form a x 10".
Example: 3000 = 3.0 × 103.
Accuracy: How close a measured value is to the true value.
Precesion: How consistently measurements can be operated.
Exampel: A clock showing the correct time is accurate, If it always shows the same time (even if wrong) it precise.
The Sl system provides a standarized, universally accepted system of measurement, ensuring consistency and accuracy across all scientific and engineering fields worldwide.
✩ Base Quantities: Fundamental quantities not derived from others., (e.g., length, time).
Example: length (meter), Time (second).
Example: Speed = distance/time (m/s).
Derived Quantities: Formed by combining base quantities mathematically.
They are classified into:
Ans. Physical quantities are measurable aspects of nature used to describe physical phenomena
B. Base Quantities: Fundamental and independent (e.g., length, mass and time).
b. Derived Quantities: Demental and
