Measurement

Samacheer Book Back Questions And Answers For Science Standard 8 “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

2. Electric current belongs to _____ quantities
(a) Base
(b) Supplementary
(c) Derived
(d) Professional

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

4. Luminous intensity is the intensity of
(a) Laser light
(b) UV light
(c) Visible light
(d) IR light

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

6. 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.

II. Fill in the blanks:
1. The solid angle is measured in _____.
2. The coldness or hotness of a substance is expressed by _____.
3. _____ is used to measure electric current.
4. One mole of a substance contains _____ atoms or molecules.
5. The uncertainty in measurement is called as _____.
6. The closeness of the measured value to the original value is _____.
7. The intersection of two straight lines gives us _____.

Answers:
1. Steradian
2. Temperature
3. Ammeter
4. 6.022×10²³
5. Error
6. Accuracy
7. Plane angle

III. True or False:
1. Temperature is a measure of total kinetic energy of the particles in a system.
2. If one coulomb of charge is flowing in one minute, it is called ‘ampere’.
3. Amount of substance gives the number of particles present in the substance.
4. Intensity of light from a candle is approximately equal to one ‘candela’.
5. Quartz clocks are used in GPS Devices.
6. Angle formed at the top of a cone is an example for ‘plane angle’.
7. The number 4.582 can be rounded off as 4.58.

Answers:
1. False (Temperature is a measure of average kinetic energy of the particles in a system)
2. False (One coulomb of charge flowing per second is called ampere)
3. True
4. True
5. False (Atomic clocks are used in GPS Devices)
6. True
7. True

IV. Match the following:
1. Temperature       A. Closeness to the actual value
2. Plane angle         B. Measure of hotness or coldness
3. Solid angle          C. Closeness to two or more measurements
4. Accuracy              D. Angle formed by the intersection of three or more planes
5. Precision              E. Angle formed by the intersection of two planes

Answers:
1. B
2. E
3. D
4. A
5. C

V. Assertion & Reason:
1. Assertion: The SI system of units is the suitable system for measurements.
Reason: The SI unit of temperature is kelvin.
(a) Both assertion and reason are true and reason is the correct explanation of the assertion.
(b) 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) Both assertion and reason are false.

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

3. 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.
(a) Both assertion and reason are true and reason is the correct explanation of the assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) Assertion is false, but reason is true.
(d) Both assertion and reason are false.

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