Samacheer Kalvi 8th Science Unit 1 Answers

Samacheer Kalvi 8th Science Unit 1 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2023 to 2024 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 1 – Measurement Answers Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 1 Answers are given below.

Science Book Back Answers

Unit 1 – Measurement

I. Choose the best answer

1. Which one the following system of units is the British System of unit?
(a) CGS
(b) MKS
(c) FPS
(d) SI
Answer:
(c) FPS

2. Electric current belongs to …………… quantities
(a) Base
(b) Supplementary
(c) Derived
(d) professional
Answer:
(a) Base

3. SI unit of temperature is
(a) Celsius
(b) Fahrenheit
(c) kelvin
(d) Ampere
Answer:
(c) kelvin

4. Amount of substance is
(a) Directly proportional to the number of atoms
(b) Inversely proportional to the number of atoms
(c) Directly proportional to the square of number of atoms
(d) Inversely proportional to the square of number of atoms
Answer:
(a) directly proportional to the number of atoms

5. Luminous intensity is the intensity of
(a) Laser light
(b) UV light
(c) Visible light
(d) IR light
Answer:
(c) visible light

6. Which one of the following devices is used to measure electric current
Answer:

7. SI unit stands for
(a) International system of units
(b) Integrated System of units
(c) International symbol of units
(d) Integrated symbol of units
Answer:
(a) International system of units

8. Closeness of two or more measured values is called as
(a) Accuracy
(b) Precision
(c) Error
(d) Approximation
Answer:
(b) Precision

9. Quantities other than base quantities are called as
(a) Supplementary quantities
(b) Derived quantities
(c) Professional quantities
(d) Energy quantities
Answer:
(b) Derived quantities

10. Which of the following statements about approximation is wrong?
(a) Approximation gives accurate value.
(b) Approximation simplifies the calculation.
(c) Approximation is very useful when little information is available.
(d) Approximation gives the nearest value only.
Answer:
(a) Approximation gives accurate value.

II. Fill in the blanks

The solid angle is measured in ……………
…………….. recognized the need of ‘Standard Units’ for physical quantities.
The coldness or hotness of a substance is expressed by ……………..
…………….. is used to measure electric current.
……………… of substance, contains 6.023 x 10⁺²³atoms or molecules.
Luminous Intensity is the amount of visible light, that is emitted in unit area per unit …………….
Quartz clock uses …………….. oscillations.
The uncertainty in measurement is called as …………….
……………… is the closeness of the measured value to the original value.
The intersection of two straight lines gives us ……………….

Answer:

Steradian
Scientists
Temperature
Ammeter
One mole
Solid angle
Electronic
Error
Accuracy
plane angle

III. True or False

1. SI units are metric system of units.
Answer:
True

2. Temperature is a measure of total kinetic energy of the particles in a system.
Answer:
False
Correct statement:
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.
Answer:
False
Correct statement:
In thermometers, boiling point of water is taken as the Upper Fixed Point.

4. One coulomb of charge flowing per minute is called ‘ampere’.
Answer:
False
Correct statement:
One coulomb of charge flowing per second is called ‘ampere’.

5. Amount of substance gives the number of particles present in the substance.
Answer:
True

6. Intensity of light from a candle is approximately equal to one ‘candela’.
Answer:
True

7. Angle formed at the top of a cone is an example of ‘Plane Angle’.
Answer:
True

8. Quartz clocks are used in GPS Devices.
Answer:
False
Correct statement:
Atomic clocks are used in GPS Devices.

9. Candela is used to express electric field intensity.
Answer:
False
Correct statement:
Candela is used to express luminous intensity.

10. The number 4.582 can be rounded off as 4.58.
Answer:
True

IV. Match the following

Answer:

1 – b: 2 – e: 3 – d: 4 – a: 5 – c

V. Consider the statements given below and choose the correct option.

Mark the correct choice as

(a) If both assertion and reason are true and reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) Assertion is true, but reason is false.
(d) 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.
Answer:
(b) Both assertion and reason are true but reason is not the correct explanation of the assertion
Correct explanation :
In the SI system, the units are precisely defined and have the same value everywhere.

2. Assertion: Electric current, amount of substance, and Luminous Intensity are the fundamental physical quantities.
Reason: They are independent of each other.
Answer:
(a) Both assertion and reason are true and reason is the correct explanation of the assertion

3. Assertion: The second 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.
Answer:
(c) Assertion is true, but reason is false
Correct explanation :
Least count is the minimum measurement that can be measured accurately by an instrument.

4. Assertion: Avogadro’s number is the number of atoms in one mole of a substance.
Reason: Avogadro’s number is a constant.
Answer:
(a) Both assertion and reason are true and reason is the correct explanation of the assertion

5. Assertion: Radian is the unit of solid angle.
Reason: One radian is the angle subtended at the center of a circle by an arc of length equal to its radius.
Answer:
(d) Assertion is false, but reason is true]
Correct explanation :
Radian is the unit of plane angle.

VI. Answer in a word or two (Very Short Answer)

1. What is the unit of mass in the FPS system?
Answer:
Pound.

2. How many base quantities are included in the SI system?
Answer:
Seven.

3. Give the name of the instrument used for the measurement of temperature.
Answer:
Thermometer.

4. What is the ‘Lower Fixed Point’ of the Fahrenheit scale?
Answer:
32°F.

5. What is the SI unit of Luminous Intensity?
Answer:
Candela (cd).

6. What is the value of Avogadro’s number?
Answer:
6.023 x 1023.

7. What type of oscillations are used in atomic clocks?
Answer:
Periodic vibrations.

8. Mention the types of clocks based on their display.
Answer:
Analog clock and digital clock.

9. How many times will the ‘minute hand’ rotate in one hour?
Answer:
One time.

10. How many hours are there in a minute?
Answer:
60 minutes = 1 hr
1 minute = 160 = 0.0167 hours.

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22 Apr 2022