Units and Measurement Infographic

Unit and Measurement

📐Core Concepts

Physical Quantity

Anything that can be measured directly or indirectly. The fundamental properties of our universe.

Unit

A standard used for making comparisons in measurements. It gives numbers a physical meaning.

Measurement

The process of connecting numbers with physical quantities and phenomena.

Metrology

The scientific study of measurement. The science of precision and accuracy.

🌐Systems of Units

CGS

C.G.S

Centimeter Gram Seconds

FPS

F.P.S

Foot Pound Seconds

MKS

M.K.S

Meter Kilogram Seconds

SI

S.I

International System

🧭Classification by Magnitude & Direction

🔢Scalar Quantity

A physical quantity which has only magnitude but no direction.

Examples: Mass, speed, time, work, temperature.

➡️Vector Quantity

A physical quantity which has both magnitude as well as direction.

Examples: Velocity, weight, momentum, displacement.

🧱Classification by Units & Measurements

🏛️Fundamental Quantity

Physical quantities which are independent of other physical quantities.

Examples: Length, mass, time etc.

🏗️Derived Quantity

Physical quantities which are dependent on fundamental quantities.

Examples: Speed, velocity, area etc.

Fundamental Quantities and Units (SI)

S.NPhysical QuantityUnitAbbreviation
1MassKilogramkg
2LengthMeterm
3TimeSecondsec
4TemperatureKelvinK
5Amount of substanceMolemol
6Electric currentAmpereA
7Luminous intensitycandelacd

📋Common Physical Quantities and Units

Electric current: Ampere (A)

Volume: Cubic metre (m³)

Temperature: Kelvin (K)

Area: Metre square (m²)

Amount of substance: Mole (mol)

Electric power: Kilowatt (KW)

Force: Newton (N)

Radioactivity: Currie

Pressure: Pascal (Pa)

Earthquake: Rictor (Richter)

Work / energy: Joule (J)

Heat: Joules

Power: Watt (W)

Length (atomic): Angstrom (Å)

Angle: Radians (Rad)

Purity of gold /Gems: Carat

Frequency: Hertz (Hz)

Speed: Meter/sec (m/s)

Charge: Coulomb (C)

Displacement: Meters (m)

Resistance: Ohm (Ω)

Intensity of sound: Decibels (dB)

Power of lens: Dioptre (D)

Solar distance: Light year

Inductance: Henry (H)

Potential difference/voltage: Volt (V)

Conductance: Farad (F)

Velocity: Meter/sec (m/s)

Viscosity: Poise

Acceleration: Metre/sec² (m/s²)

Resistivity: Ohm-metre (Ω·m)

Impulse: Newton-second (N·s)

🔟Exponents of 10: Prefixes

Positive Powers (Large Scale)

10²¹ Zetta (Z)

10¹⁵ Peta (P)

10¹² Tera (T)

10⁹ Giga (G)

10⁶ Mega (M)

10³ Kilo (k)

Negative Powers (Small Scale)

10⁻² Centi (c)

10⁻³ Milli (m)

10⁻⁶ Micro (µ)

10⁻⁹ Nano (n)

10⁻¹⁰ Angstrom (Å)

10⁻¹² Pico (p)

10⁻¹⁵ Femto/Fermi (f)

10⁻²¹ Zepto (z)

🔬Scientific Instruments & Applications

Ammeter

Measures electric current.

✈️

Altimeter

Measures altitude in aircraft.

🌬️

Barometer

Measures atmospheric pressure.

submarine

Periscope

To see objects above eye level.

🌡️

Thermometer

Measures temperature.

🔋

Voltmeter

Measures potential difference (voltage).

🔌

Transformer

Reduces or increases electric current.

💧

Hygrometer

Measures humidity in the air.

⚙️

Dynamo

Converts mechanical to electrical energy.

💡

Motor

Converts electrical to mechanical energy.

🍯

Viscometer

Measures viscosity in liquids.

🍃

Anemometer

Records wind velocity.

Carburettor

Mixes petrol vapours and air.

⏱️

Chronometer

Measures accurate time.

📽️

Epidiascope

Projects films and images.

🔥

Calorimeter

Measures heat generated by fuels.

🌊

Fathom-meter

Measures depth of the Ocean.

⚖️

Hydrometer

Measures specific gravity of liquids.

🔊

Hydrophone

Records underwater sound.

🥛

Lactometer

Measures purity of milk or any liquids.

📣

Megaphone

Carries sound over long distances.

🎤

Microphone

Measures or records sound.

📏

Micrometer

Measures very small length (LC 0.001cm).

📐

Vernier caliper

Measures a small length (LC 0.01 cm).

💨

Manometer

Measures pressure of gas.

🔬

Microscope

Magnifies micro-objects (10⁻³).

☢️

Radiometer

Measures radiation energy.

🌡️

Thermostat

Regulates temperature.

Thermocouple

Measures temperature by change in electric current.

🔭

Telescope

Observes distant or heavenly objects.

☀️

Pyrometer

Records high temperature at a great distance.

🎶

Phonograph

For reducing sound (likely means ‘reproducing’).

☀️

Photovoltaic cell

Converts photo (light) energy into electrical energy.

💡

Photometer

Measures intensity of light.

💧

Hygrometer

Measures humidity in the air.

🧭

Sextant

Measures angular elevation.

🗺️

Theodolite

Measures horizontal and vertical angles.

🔮

Spherometer

Measures small thickness / curvature.

🚗

Odometer

Measures the distance covered by vehicles.

🛰️

Telstar

Transmits television broadcast across continents.

💡Important Points

  1. Measure of Frequency is Hertz.
  2. Kilowatt-hour is Unit to measure Electrical Energy.
  3. In a photocell, light is converted into Electrical energy.
  4. Instrument to see heavenly bodies: Telescope.
  5. A generator is a device that generates Electrical energy.
  6. Instrument to measure electric current is Ammeter.
  7. Unit of measuring electrical resistance: Ohm.
  8. Decibel is the unit of Sound intensity.
  9. Power of a lens is measured in Diopters.
  10. The ship’s speed is measured in Knots.
  11. Intensity of light is measured with a Photometer.
  12. The unit of pressure is Pascal.
  13. Ampere is a unit of current.
  14. The unit of surface tension is Newton/meter.
  15. The unit of energy in the SI is Joule.
  16. The unit of density in CGS is Gram per cubic centimeter.
  17. A device that converts electrical energy into mechanical energy is an electric motor.
  18. The SI unit of wavelength is Meter.
  19. The unit of force is Newton.
  20. The term Ton is used for weight.
  21. Unit of density in CGS is g/cm³.
  22. Electrical energy is converted into light energy inside a photocell.
  23. Nanometre is equal to 10⁻⁹ meter.
  24. Instrument measuring the purity of milk is lactometer.
  25. The SI unit of resistance is Ohm.
  26. Speed is a scalar quantity.
  27. The unit of energy in SI is Joule.
  28. The unit of weight is Newton.
  29. Length, mass, and time are fundamental units.
  30. Dyne*cm/sec is the unit of power.
  31. 1 Newton is equal to 10⁵ dyne.
  32. 1 joule is equal to 10⁷ erg.
  33. SI unit of density is Kg/m³.
  34. Vernier caliper is used for measuring length.
  35. 1 gallon is equal to 4.546 liters.
  36. The unit of work is Joule.
  37. Speed of light is 3×10⁸ m/s.
  38. Units of temperature are Celsius, Fahrenheit, Kelvin.
  39. SI unit of power of lens is diopter.
  40. Unit of pressure is Newton per meter square.
  41. Bar is the measurement unit of atmospheric pressure.
  42. The unit of radioactivity is Curie.
  43. The unit of specific resistance is Ohm-m.
  44. Ampere hour is the unit of charge.
  45. Unit of electric charge is coulomb.
  46. Specific gravity of liquid is tested by hydrometer.

Check Your Knowledge (MCQs)

1. The SI unit of power is

  • a. Ampere
  • b. Coulomb
  • c. Watt
  • d. Joule

2. The loudness of sound is measured in

  • a. Joule
  • b. Meter / second
  • c. Decibel
  • d. Hours

3. The unit of measuring Astronomical Distance is

  • a. Kilometer
  • b. Meter
  • c. Light year
  • d. Nautical Mile

4. What is the unit of Resistance?

  • a. Coulomb
  • b. Ampere
  • c. Ohm
  • d. Watt

5. The SI unit of power of lens is

  • a. Dioptre
  • b. Watt
  • c. Candela
  • d. Joule

6. What is the SI unit of mass?

  • a. Gram
  • b. Milligram
  • c. Kilogram
  • d. Centigram

7. The device used to measure the humidity of liquids (Note: text likely means ‘specific gravity of liquids’ or ‘humidity of air’)

  • a. hydrometer
  • b. hygrometer
  • c. hydrophone
  • d. lactometer

8. What is the SI unit of weight?

  • a. Kg/s²
  • b. Kg m/s
  • c. Kg
  • d. Newton

9. Unit for measuring energy

  • a. Joule
  • b. Newton
  • c. Decibel
  • d. Ampere

10. Ampere is a unit of

  • a. Magnetic field
  • b. Electric charge
  • c. Light intensity
  • d. Electric current

11. The ‘parsec’ is the unit of

  • a. Distance
  • b. Time
  • c. Energy
  • d. Temperature

12. What is the SI unit of thermodynamic temperature?

  • a. Kelvin.
  • b. Hertz
  • c. Ampere
  • d. Candela

13. The unit Nautical mile per hour is used to measure the speed of which of the following?

  • a. Maglev
  • b. Leopards
  • c. Bullet Train
  • d. Ship

14. The SI Unit of Charge is –

  • a. Ampere
  • b. Volt
  • c. Coulomb
  • d. Ohm

15. Density of the material of a substance is its mass divided by

  • a. surface area
  • b. volume
  • c. specific gravity
  • d. square of surface area

16. The physical quantities which has magnitude only and direction is not considered is called

  • a. Vector
  • b. scalar
  • c. fundamental
  • d. derived

17. Which of the following is not a vector quantity?

  • a. Speed
  • b. velocity
  • c. torque
  • d. displacement

18. Calorie is the unit of

  • a. Length
  • b. temperature
  • c. heat
  • d. mass

19. Kilowatt hour is the unit of

  • a. Potential difference
  • b. electric power
  • c. electric energy
  • d. electric potential

20. The SI unit of frequency

  • a. ampere
  • b. hertz
  • c. heat
  • d. kelvin

21. One micron is equal to

  • a. 0.1mm
  • b. 0.001mm
  • c. 0.0001
  • d. 0.00001mm

22. 1 joule is equal to

  • a. 10^7 erg
  • b. 10^2 erg
  • c. 10^5erg
  • d. 10erg

23. How many watts are there in 1 horsepower

  • a. 746
  • b. 360
  • c. 180
  • d. 476

24. What is the unit of specific resistance

  • a. ohm
  • b. ohm-meter
  • c. ohm-sec
  • d. ohm/cm

25. Which of the following is not the unit of energy

  • a. Newton-meter
  • b. kilowatt hour
  • c. joule
  • d. megawatt

26. What is the SI unit pressure

  • a. pascal
  • b. watt
  • c. joule
  • d. none

27. The unit of power is

  • a. joule per second
  • b. joule
  • c. joule per second and watt
  • d. none

28. Purity of milk is measured by which equipment

  • a. hydrometer
  • b. barometer
  • c. lactometer
  • d. none

29. SI unit of force

  • a. Pascal
  • b. hertz
  • c. meter
  • d. newton

30. The specific gravity of liquid is measured by

  • a. thermometer
  • b. hydrometer
  • c. barometer
  • d. hygrometer

31. A light year is a unit of

  • a. time
  • b. speed of light
  • c. distance
  • d. intensity of light

32. The quantity which has both magnitude and direction is known as

  • a. scalar
  • b. variable
  • c. real
  • d. vector

33. Radian is the SI unit of

  • a. solid angle
  • b. plane angle
  • c. acute angle
  • d. straight angle

34. Which among the following is a fundamental quantity

  • a. mass
  • b. volume
  • c. velocity
  • d. force

35. Ampere is the SI unit of

  • a. electric charge
  • b. electric current
  • c. electric potential
  • d. electric resistance

36. Newton-sec is the unit of

  • a. impulse
  • b. momentum
  • c. energy
  • d. force

37. Which instrument is used to measure the atmospheric pressure

  • a. lactometer
  • b. barometer
  • c. ammeter
  • d. hygrometer

38. The unit of surface tension is

  • a. Newton
  • b. newton/m
  • c. newton-meter
  • d. newton-sec

39. The unit of speed in seawater is

  • a. km/h
  • b. m/sec
  • c. knot
  • d. light year
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