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VIII-EM-MEASUREMENT Q & A
MEASUREMENT
I. CHOOSE THE BEST ANSWER
1. Which one of the following systems of units is the British System of unit?
a) CGS b) MKS
c) FPS d)SI
Ans : c) FPS
2. Electric current belongs to _______ quantities
a) base b) supplementary
c) derived d)professional
Ans : a) base
3. SI unit of temperature is
a) Celsius b) Fahrenheit
c) Kelvin d) Ampere
Ans : c) Kelvin
4. Luminous intensity is the intensity of
a) Laser light b) UV light
c) visible light d) IR light
Ans : c) visible light
5. Closeness of two or more measured values is called as
a) accuracy b) precision
c) error d) approximation
Ans : b) precision
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.
Ans : a) Approximation gives accurate value
II. FILL IN THE BLANKS.
The solid angle is measured in __________________.
Ans : steradian
The coldness or hotness of a substance is expressed by_________________.
Ans : temperature
_____________________ is used to measure electric current.
Ans : Ammeter
One mole of substance, contains__________________ atoms or molecules.
Ans: 6.023 × 1023
The uncertainty in measurement is called as _________________.
Ans : errors
6. The closeness of the measured value to the original value is ______________.
Ans : Accuracy
7. The intersection of two straight lines gives us _____________.
Ans : 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
Ans : False.
Temperature is a measure of average kinetic energy of the particles in a system
If one coulomb of charge is flowing in one minute it is called 'ampere'.
Ans : False.
One coulomb of charge flowing per second is called ‘ampere’.
Amount of substance gives the number of particles present in a substance.
Ans : True
Intensity of light from a candle is approximately equal to one 'candela'.
Ans : True
5.Quartz clocks are used in GPS Devices.
Ans : False.
Atomic clocks are used in GPS Devices
6. Angle formed at the top of a cone is an example of 'Plane Angle'.
Ans : False.
Angle formed at the top of a cone is an example of 'Solid Angle’.
7. The number 4.582 can be rounded off as 4.58 .
Ans : True
IV. MATCH THE FOLLOWING.
Ans:
V. 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.
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.
Ans : a) 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.
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.
Ans : c) Assertion is true, but reason is 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.
Direction: 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.
Ans : d) Assertion is false, but reason is true.
VI. ANSWER VERY BRIEFLY.
1. How many base quantities are included in the SI system?
Ans : There are seven base quantities in SI system.
2. Give the name of the instrument used for the measurement of temperature.
Ans : The instrument used for the measurement of temperature is thermometer.
3. What is the SI unit of Luminous Intensity?
Ans : The SI unit of luminous intensity is candela.
4. What type of oscillations are used in atomic clocks?
Ans : Periodic vibrations occurring within the atom
5. Mention the types of clocks based on their display.
Ans : The types of clocks based on their display are
Analog clocks,
Digital clocks
6. How many times will the 'minute hand' rotate in one hour?
Ans :Minute hand rotates 60 times to make one hour
7. How many hours are there in a minute?
Ans : 1/60 = 0.0167 hours
VII. ANSWER BRIEFLY
1. What is measurement?
Measurement is the process of finding an unknown physical quantity by using a standard quantity.
2. Name the three scales of temperature.
The three scales of temperature are
a. Celsius
b. Fahrenheit
c. Kelvin
3. Define - Ampere.
When one coulomb of charge is flowing through a conductor in one second, then the current flowing through the conductor is said to be an ampere.
4. What is electric current?
Flow of electric charges, in a particular direction is known as 'electric current'.
Amount of electric charge
Electric current = -----------------------------------------
Time
5. What do you mean by 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.
6. Define - Mole.
Mole is defined as the amount of substance, which contains 6.023 x 1023 entities.
7. What are the differences between Plane angle and solid angle?
VIII. ANSWER IN DETAIL
1. List out the base quantities with their units.
2. Write a short note on different types of clocks.
a) Based on display:
We can classify clocks based on display into two types. They are analog clock and digital clock.
(i) Analog clocks:
It looks like a classic clock. It has three hands to show the time.
Hours Hand: It is short and thick. It shows 'hour'.
Minutes Hand: It is long and thin. It shows 'minute'
Seconds hand: It is long and very thin. It shows 'second'. It makes one rotation in one minute and 60 rotations in one hour.
Analog clocks can be driven either mechanically or electronically
(ii) Digital clocks
A digital clock displays the time directly. It shows the time in numerals or other symbols. It may have 12 hours or 24 hours display.
Recent clocks are showing Date, Day, Month, Year, Temperature etc.
Digital clocks are often called as Electronic Clocks.
b) Based on working mechanism:
We can classify clocks based on mechanism into two types. They are quartz clock and atomic clock.
1. Quartz clock :
These clocks are activated by 'electronic oscillations', which are controlled by a 'quartz crystal'.
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.
2. Atomic clock :
These clocks are making use of periodic vibrations occurring within the atom.
These clocks have an accuracy of one second in every 1013 seconds.
Atomic clocks are used in (Global Positioning System (GPS), Global Navigation Satellite System (GLONASS) and International Time Distribution services.
IX. 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 100oC. Is it possible to have 100oC fever? If it is wrong, try to make him to understand.
Ans : No, it is not possible for 100oC fever. The normal temperature of the human body is between 98.4oF and 98.6o F. In addition, the clinical thermometer is also graduated in 'Fahrenheit scale' only. So, he has to say he was affected by a fever of 100oF and not 100oC.
