Samacheer Kalvi 8th Science Solutions Chapter 1 Pdf
Tamilnadu Board Samacheer Kalvi 8th Science Solutions Chapter 1: Tamilnadu State Board Solution Class 8 Science Chapter 1 – Measurement.
Samacheer Kalvi 8th Science Solutions Chapter 1: Overview
|
Board |
Samacheer Kalvi |
| Class |
8 |
|
Subject |
Science |
| Chapter |
1 |
|
Chapter Name |
Measurement |
Samacheer Kalvi 8th Science Solutions Chapter 1 Pdf
Choose the best answer.
1.) Which one of the following systems of unit is the British System of unit ?
a.) CGS b. MKS c. FPS d. SI
Answer : FPS
2.) Electric current is a base quantity
a) base
b) supplementary
c.) derived
d. professional
3.) SI unit of temperature is Kelvin
a.) celsius b. fahrenheit
c.) Kelvin d. ampere
4.) Luminous intensity is the intensity of visible light.
a.) laser light b. UV light
c.) visible light d. IR light
5.) Closeness of two or more measured values is called as precision
a.) accuracy b. precision
c.) error d. approximation
6.) Which 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.
Answer
a.) Approximation gives accurate value.
Explanation :
Option A is wrong. We are all aware of the fact that, approximation does not provide us accurate value.
Fill in the blanks.
1.) The solid angle is measured in Steradian .
2.) The coldness or hotness of a substance is expressed by Temperature
3.) Ammeter is used to measure electric current.
4.) One mole of a substance contains6.023×1023atoms or molecules.
5.) The uncertainty in measurement is called asError
6.) The closeness of the measured value to the original value is Accuracy
7.) The intersection of two straight lines gives usPlane Angle
State true or false. If false, correct the statement.
1.) Temperature is a measure of total kinetic energy of the particles in a system.
This statement is false.
Explanation:
Temperature is not a measure of total kinetic energy of the particles in a system but rather it is a measure of average kinetic energy of the particles in a system. There is an increase in the motion of these particles, when there is an increase in temperature.
2.) If one coulomb of charge is flowing in one minute, it is called ‘ ampere’ .
This statement is false.
Explanation:
When one coulomb of charge flows in one second, then it is termed as ampere.
3.) Amount of substance gives the number of particles present in a substance.
This statement is true.
4.) Intensity of light coming from a candle is approximately equal to one‘candela’.
This statement is true.
5.) Quartz clocks are used in GPS devices.
This statement is false.
Explanation:
In GPS devices, Atomic clocks are used.
6.) Angle formed at the top of a cone is an example for ‘ plane angle’.
This statement is false.
Explanation :
Angle which is created at the topmost of a cone, depicts an example for ‘solid angle’.
7.) The number 4.582 can be rounded off as 4.58
This statement is 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 |
Answer :
| 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 |
Consider the statements given below and choose the correct option.
1.) Assertion : The SI System of units is the suitable system for measurements.
Reason : The SI unit of temperature is Kelvin .
Answer
Both assertion and reason are true but reason is not the correct explanation of the assertion .
Explanation :
The units are accurately explained in the SI system and contains the similar value in every direction.
2.) Assertion : Electric current, amount of substance, luminous intensity are the fundamental physical quantities.
Reason: They are independent of each other.
Answer
Both assertion and reason are true and reason is the correct explanation of the assertion.
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.
Answer
Assertion is false but reason is true.
Explanation:
Radian is not the unit of solid angle but instead, it is the unit of plane angle. Therefore, the assertion is incorrect.
Answer very briefly.
1.) How many base quantities are included in SI system?
Answer: Seven
Explanation:
The SI system is composed of seven base quantities that elucidate the twenty two derivational quantities with distinct names and symbols. The SI performs an important function in international commerce and is mainly used for the purpose of scientific and technical investigations.
2.) Give the name of the instrument used for the measurement of temperature.
Answer : Thermometer
Explanation:
Thermometer is an instrument that is used for the purpose of measuring temperature. Celsius Fahrenheit and Kelvin are for instance , the most common units of temperature measurement.
3.) What is the SI unit of luminous intensity?
Answer : Candela is the SI unit of luminous intensity.
Explanation:
In the International System of Units, Candela represents the base unit of luminous intensity, which means incandescent power for each unit solid angle transmitted by a point source of light in a specific direction.
4.) What type of oscillations are used in atomic clocks?
Answer : Periodic vibrations are used in atomic clocks.
Explanation:
Atomic clock is also known as cesium clock. Atomic clocks are mainly used for the purpose of tracking satellites ,operating navigation system and analysing Earth’s outermost motions .The periodic vibration that are formed within the cesium atom gives the foundation of the atomic clock.
5.) Mention the types of clocks based on their display.
Clocks employs various distinct ways in order to display the time. In Analog clock, time are indicated with a conventional clock face , with movable hands. Digital clock exhibits a numerical depiction of time.
6.) How many times will the ‘minute hand’ rotate in one hour?
Answer : The ‘minute hand’ will rotate only once in one hour.
Explanation:
The ‘minute hand ‘completes one revolution within a period of one hour.
7.) How many hours are there in a minute?
Answer : 0.0167 hours
Explanation:
As we all know that, 60 minutes is equivalent to 1 hour . So, 1 minute is equivalent to 1/60 which is then equal to 0.0167 hours . Therefore, 0.0167 hours are there in a minute.
Answer briefly.
1.) What is measurement?
Measurement provides the base for every scientific methods and investigations. It performs an essential function in our day to day life. It is the process which utilizes a standard quantity in order to find out an unknown physical quantity.
2.) Name the three scales of temperature.
The measure of the average kinetic energy of the particles in a system is termed as temperature. Kelvin is the SI unit of temperature. In order to measure the temperature directly, thermometers are used. Which some standard scales, thermometers are calibrated. The most commonly used scales for measuring temperature are Celsius, Fahrenheit and Kelvin.
3.) Define- Ampere .
When there is a flow of one coulomb of charge through a conductor in one second, then the quantity of current that is flowing is termed as one ampere. Ammeter is an instrument that is used for the purpose of measuring ‘electric current’.
4.) What is electric current?
If the electric charges flow in a specific direction, then it is termed as ‘electric current’. The quantity of electric charges moving through a conductor in one second is the magnitude of electric current. Coulomb is the measuring unit of electric charge. Ampere is the SI unit of electric current.
5.) What do you mean by luminous intensity?
The measurement of the power of the transmitted light, by a source of light in a specific direction, for each unit solid angle is termed as luminous intensity. Candela is the SI unit of luminous intensity. The emission of light from a common wave candle is almost equivalent to one candela. Photometer is a Luminous Intensity Meter which measures luminous intensity and provides the luminous intensity in the context of candela directly.
6.) Define- Mole
The quantity of substance, containing 6.023× 10 23 entities is termed as Mole. It is usually indicated as ‘ mol’ .
7.) What are the differences between plane angle and solid angle?
Difference between plane angle and solid angle
Plane Angle
- The angle which is constructed at the intersection point of two planes or lines is known as plane angle.
- It involves two dimensions.
- Radian is the unit of Plane Angle.
Solid Angle
- The angle which is constructed at the intersection point of three or more planes is known as solid angle.
- It involves three dimensions.
- Steradian is the unit of Solid Angle.
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.
Based on display, there are two types of clocks:
i.) Analog clocks
ii.) Digital clocks
i.) Analog clocks bears resemblance to a classic clock. It consists of three hands in order to display the time.
Hours hand
It is small and not very thin. It displays ‘ hour’ .
Minute hand
It is thin and not very short. It displays ‘ minute’ .
Seconds hand
It is extremely thin and not very short. It displays ‘ second ‘ . In one minute , it completes one rotation and in one hour it completes 60 rotations.
Analog clocks can be operated both mechanically or electronically.
2.) Digital clocks
The time are showed directly by a digital clock. The time are displayed in numeric or other symbols. It might have a display of 12 hours or 24 hours. Date , day, month, year, temperature etc are shown by recent clocks. Digital clocks are also known as electronic clocks.
Based on working mechanism, there are two types of clocks :
i.) Quartz clock
ii.) Atomic clock
i.) Quartz clock
Electronic oscillations provides activation to these clocks and are regulated by a’ quartz crystal’ . There is a precision in the frequency of a vibrating crystal. Therefore, quartz clock seems to be more accurate when compared to mechanical clock. In every 10 seconds , these clocks depicts an accuracy of one second.
ii.) Atomic clock
Periodic vibrations are used by these clocks that occur within a casium atom. In every 1013 seconds, these clocks depicts an accuracy of one second. These clocks are used in various systems , like Global Positioning System, Global Navigation Satellite System and International Time DistributionServices.
Higher Order Thinking Question.
1.) Your friend was absent to school yesterday. You are enquiring about his absence. He told that he had fever and it was measured to be 100 ° C. Is it possible to have 100 ° C fever ? If he is wrong, try to make you understand.
A person cannot have 100°C fever because it is not feasible to have so. The normal body temperature of an individual is usually between 98.4 ° F and 98.6 ° F . So, it would be correct to say, that he had fever and it was measured to be 100 °F .
