Lesson 1. Measurement
Lesson 1. Measurement
I. Choose the best answer
1. Which one the following system of units is the British System of unit?
- CGS
- MKS
- FPS
- SI
Ans : FPS
2. Electric current belongs to ______ quantities
- base
- supplementary
- derived
- professional
Ans : base
3. SI unit of temperature is
- celsius
- fahrenheit
- kelvin
- ampere
Ans : kelvin
4. Amount of substance is
- directly proportional to the number of atoms
- inversely proportional to the number of atoms
- directly proportional to the square of number of atoms
- inversely proportional to the square of number of atoms
Ans : directly proportional to the number of atoms
5. Luminous intensity is the intensity of
- Laser light
- UV light
- visible light
- IR light
Ans : visible light
6. Which one of the following devices is used to measure electric current
Ans : b
7. SI unit stands for
- International system of units
- Integrated System of units
- International symbol of units
- Integrated symbol of units
Ans : International system of units
8. Closeness of two or more measured values is called as
- accuracy
- precision
- error
- approximation
Ans : precision
9. Quantities other than base quantities are called as
- supplementary quantities
- derived quantities
- professional quantities
- energy quantities
Ans : derived quantities
10. Which of the following statements about approximation is wrong?
- Approximation gives accurate value.
- Approximation simplifi es the calculation.
- Approximation is very useful when little information is available.
- Approximation gives the nearest value only.
Ans : Approximation gives accurate value.
II. Fill in the blanks.
1. The solid angle is measured in _______.
Ans : steradian
2. _______ recognized the need of ‘Standard Units’ for physical quantities.
Ans : International system of units
3. The coldness or hotness of a substance is expressed by _______.
Ans : temperature
4. _______ is used to measure electric current.
Ans : Ammeter
5. _______ of substance, contains 6.023 × 10+23 atoms or molecules.
Ans : One mole
6. Luminous Intensity is the amount of visible light, that is emitted in unit area per unit _______.
Ans : solldangle
7. Quartz clock uses _______ oscillations.
Ans : electronic
8. The uncertainty in measurement is called as _______.
Ans : errors
9. _______ is the closeness of the measured value to the original value.
Ans : Accuracy
10. The intersection of two straight lines gives us_______.
Ans : plane angle
III. True or False.
1. SI units are metric system of units.
Ans : True
2. Temperature is a measure of total kinetic energy of the particles in a system.
Ans : False
Cu. An. : Temperature is a measure of average kinetic energy of the particles in a system.
3. In thermometers, freezing point of water is taken as the Upper Fixed Point.
Ans : False
Cu. An. : In thermometers, bollling point of water is taken as the Upper Fixed Point.
4. One coulomb of charge flowing per minute is called ‘ampere’.
Ans : False
Cu. An. : One coulomb of charge flowing per second is called ‘ampere’
5. Amount of substance gives the number of particles present in the substance.
Ans : True
6. Intensity of light from a candle is approximately equal to one ‘candela’.
Ans : True
7. Angle formed at the top of a cone is an example of ‘Plane Angle’.
Ans : False
Cu. An. : Angle formed at the top of a cone is an example of ‘Solld Angle’.
8. Quartz clocks are used in GPS Devices.
Ans : False
Cu. An. : Atomic clocks are used in GPS Devices.
9. Candela is used to express electric field intensity.
Ans : False
Cu. An. : Candelais used to express light intensity.
10. The number 4.582 can be rounded off as 4.58.
Ans : True
IV. Match the following:
| 1. Temperature | Closeness to the Actual Value |
| 2. Plane Angle | Measure of hotness or coldness |
| 3. Solid Angle | Closeness to two or more measurements |
| 4. Accuracy | Angle formed by the intersection of three or more planes |
| 5. Precision | Angle formed by the intersection of two planes |
| Ans : 1 – b, 2 – e, 3 – d, 4 – a, 5 – c | |
V. Assertion & Reason.
1. Direction : Mark the correct choice as
- If both assertion and reason are true and reason is the correct explanation of the assertion.
- If both assertion and reason are true but reason is not the correct explanation of the assertion.
- Assertion is true, but reason is false.
- Assertion is false, but reason is true.
1. Assertion : The SI system of units is the suitable system for measurements.
Reason : The SI unit of temperature is kelvin.
Ans : If both assertion and reason are true and reason is the correct explanation of the assertion.
2. Assertion : Electric current, amount of substance, Luminous Intensity are the fundamental physical quantities.
Reason : They are independent of each other.
Ans : Assertion is true, but reason is false.
3. Assertion : The seconds hand of a clock is having least count of one second.
Reason : Least count is the maximum measurement that can be measured accurately by an instrument.
Ans : If both assertion and reason are true and reason is the correct explanation of the assertion.
4. Assertion : Avogadro’s number is the number of atoms in one mole of substance.
Reason : Avogadro’s number is a constant
Ans : If both assertion and reason are true but reason is not the correct explanation of the assertion.
5. Assertion : Radian is the unit of solid angle.
Reason : One radian is the angle subtended at the centre of a circle by an arc of length equal to its radius.
Ans : Assertion is false, but reason is true.
VI Answer in a word or two (Very Short Answer):
1. What is the unit of mass in FPS system?
Pound
2. How many base quantities are included in SI system?
7
3. Give the name of the instrument used for the measurement of temperature.
Thermometer
4. What is the ‘Lower Fixed Point’ of the Fahrenheit scale?
32°F
5. What is the SI unit of Luminous Intensity?
Candela
6. What is the value of Avogadro’s number?
6.023×1023
7. What type of oscillations are used in atomic clocks?
Perlodic vibrations occuring within the atom
8. Mention the types of clocks based on their display.
- Analog clocks
- Digital clocks
9. How many times will the ‘minute hand’ rotate in one hour?
one time
10. How many hours are there in a minute?
60 minutes = 1hour
VII Answer the questions given below (Short Answer):
1. What is measurement?
Measurement is the process of finding an unknown physical quantity by using a standard quantity.
2. Name some common systems of measurement.
- FPS – System (Foot for length, Pound for mass and Second for time)
- CGS -System (Centimetre for length, Gram for mass and Second for time)
- MKS – System (Metre for length, Kilogram for mass and Second for time)
3. Define- Temperature.
Temperature is a measure of the average kinetic energy of the particles in a system.
4. Define – ampere.
One ampere is defined as one ‘coulomb’ of charge moving in a conductor in one second
5. What is electric current?
- Flow of electric charges, in a particular direction is known as ‘electric current’.
- The magnitude of an electric current is the amount of electric charges flowing through a conductor in one second.
I = Q / t
6. What is luminous Intensity?
The measure of the power of the emitted light, by a light source in a particular direction, per unit solid angle is called as Luminous Intensity.
7. Define – mole.
Mole is defined as the amount of substances which contains 6.023×1023 entities.
8. What are the differences between Plane angle and solid angle?
| Plane Angle | Solid Angle |
| 1. Angle between the intersection of two lines or planes | Angle between the intersection of three or more planes at a common point |
| 2. It is two dimensional | It is three dimensional |
| 3. Unit is radian | Unit is steradian |
9. What are errors?
The value of every measurement contains some uncertainty. These uncertainties are called as ‘Errors’.
VIII Answer in detail:
1. List out the base quantities with their units.
| Quantity | Unit | Symbol |
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Temperature | kelvin | K |
| Electric Current | ampere | A |
| Amount of Substance | mole | mol |
| Luminous Intensity | candela | cd |
2. Write a short note on different types of clocks.
Types of clocks based on display:
- Analog clocks
- Digital clocks
Analog clocks:
It looks like a classic clock. It has three hands to show time.
- Hours hand: It is a short and thick it shows ‘hour’.
- Minutes hand: It is long and thin.it shows ‘minute’
- Second’s hand: it is long and very thin it shows ‘second’.it makes one rotation in one minute and 60 rotations in one hr.
Digital clocks
- A digital clocks displays the time directly. It shows the time in numerals or other symbols.
- It may have a number 12 hours or 24 hours display. Recent clocks are showing date,day,month,year,temperature,etc.,
- Digital clocks are often called as electronic clocks Types of clocks based on working mechanisms
Quartz clock:
- This clocks are activated by ‘electronic oscillations’ which are controlled by a ‘quartz crystals’
- The frequency of a vibrating crystal is very precise. So the quartz clock is more accurate than the mechanical clock.
- These clocks have an accuracy of one second in every 109 seconds.
Atomic clocks:
-
- these clocks are making use of periods vibrations occurring within the atom.
- these clocks have an accuracy of one second in every 109 seconds.
- Atoms clocks are used in global positioning system (GPS),Global Navigation satellite system (GIONASS) and international time distribution services.