if you are looking for Tamil Nadu Board Class 8 Science Chapter 1 Measurement then you are at the right place. Here we are providing solutions as well as additional QA / Important Notes.

**[I] Choose the best answer.**

Which one the following systems of unit is the British System of unit?

- a) CGS
- b) MKS
- c)
**FPS** - d) SI

Electric current is a________quantity

- a)
**base** - b) supplementary
- c) derived
- d) professional

SI unit of temperature is_____

- a) celsius
- c)
**kelvin** - b) fahrenheit
- d) ampere

Luminous intensity is the intensity of

- a) laser light
- b) UV light
- c)
**visible light** - d) IR light

Closeness of two or more measured values___is called as

- a) accuracy
- c) error
- b)
**precision** - d) approximation

Which one of the following statement 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.**

- The solid angle is measured in____[
**steradians**] - The coldness or hotness of a substance is expressed by____[
**temperature**] - ____is used to measure electric current.[
**Ammeter**] - One mole of a substance contains______atoms or molecules.[
**6.023 x 10²³**] - The uncertainty in measurement is called as_______[
**error**] - The closeness of the measured value to the original value is ________[
**accuracy**] - The intersection of two straight lines gives us ________[
**plane angle]**

**[iii] State true or false. If false, correct the statement.**

- Temperature is a measure of total kinetic energy of the particles in a system.[
**False**] - If one coulomb of charge is flowing in one minute, it is called ‘ampere.[
**False**] - Amount of substance gives the number of particles present in a substance.[
**True**] - Intensity of light coming from a candle is approximately equal to one ‘candela.[
**True**] - Quartz clocks are used in GPS devices.[
**False**] - Angle formed at the top of a cone is an example for ‘plane angle.[
**False**] - The number 4.582 can be rounded off as 4.58.[
**True**]

**[iv] Match the following.**

- Temperature – Closeness to the actual value
- Plane angle – Measure of hotness or coldness
- Solid angle – Closeness to two or more measurements
- Accuracy – Angle formed by the intersection of three or more planes
- Precision – Angle formed by the intersection of two planes

Solution:-

- Temperature – Measure of hotness or coldness
- Plane angle – Angle formed by the intersection of two planes
- Solid angle – Angle formed by the intersection of three or more planes
- Accuracy – Closeness to the actual value
- Precision – Closeness to two or more measurements

**[v] Consider the statements given below and choose the correct option.**

Assertion: The SI system of units is the suitable system for measurements.

Reason: The SI unit of temperature is kelvin.

Ans – Both assertion and reason are true but reason is not the correct explanation of the assertion.

Assertion: Electric current, amount of substance, luminous intensity are the fundamental physical quantities.

Reason: They are independent of each other.

Ans – Both assertion and reason are true and reason is the correct explanation of the assertion.

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 true, but reason is false.

**[vi] Answer very briefly.**

How many base quantities are included in SI system?

Seven base quantities.

Give the name of the instrument used for the measurement of temperature.

Thermometer

What is the SI unit of luminous intensity?

Candela (cd).

What type of oscillations are used in atomic clocks?

Periodic vibrations occurring within atoms.

Mention the types of clocks based on their display.

Analog clocks and digital clocks.

How many times will the ‘minute hand’ rotate in one hour?

Once

How many hours are there in a minute?

There are 1/60 hours in a minute.

**[vii] Answer briefly.**

What is measurement?

Measurement is the process of finding an unknown physical quantity by using a standard quantity. It involves using an instrument to determine the magnitude of a physical quantity in terms of an acceptable unit.

Name the three scales of temperature.

Celsius, Fahrenheit, and Kelvin.

Define Ampere.

Ampere is the SI unit of electric current. It is defined as the amount of electric charge passing through a conductor in one second. One ampere is equivalent to one coulomb of charge per second.

What is electric current?

Electric current is the flow of electric charges (electrons) in a particular direction through a conductor. It is measured by the amount of charge passing through the conductor per unit time.

What do you mean by luminous intensity?

Luminous intensity is the measure of the power of light emitted from a source in a particular direction, per unit solid angle. It is quantified in candelas (cd).

Define – Mole.

Mole is the SI unit of the amount of substance. It is defined as the amount of substance that contains as many entities (atoms, molecules, ions, etc.) as there are in 12 grams of carbon-12, which is approximately 6.023 x 10²³ entities (Avogadro’s number).