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SI Prefixes

In Physics, prefixes are words placed before quantities to modify their meaning. For example, when we refer to ‘sub-zero temperatures’ on a snowy day, the prefix ‘sub’ meaning ‘lower than’, we are describing temperatures lower than zero. Other common prefixes are ‘mega’ and ‘giga’, which are used every day in computing.SI units use prefixes to express especially large or small quantities. Using prefixes…

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SI Prefixes

- Astrophysics
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- Astronomical Objects
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- Classification by Luminosity
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- Cosmology
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- Circular Motion and Free-Body Diagrams
- Fundamental Forces
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- Gravity on Different Planets
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- Conservation of Energy and Momentum
- Dynamics
- Application of Newton's Second Law
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- Drag Force
- Dynamic Systems
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- Springs Physics
- Superposition of Forces
- Tension
- Electric Charge Field and Potential
- Charge Distribution
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- Conservation of Charge
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- Electric Force
- Electric Potential Due to Dipole
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- Electrical Systems
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- Electricity
- Ammeter
- Attraction and Repulsion
- Basics of Electricity
- Batteries
- Capacitors in Series and Parallel
- Circuit Schematic
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- Circuits
- Current Density
- Current-Voltage Characteristics
- DC Circuit
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- Emf and Internal Resistance
- Kirchhoff's Junction Rule
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- National Grid Physics
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- RC Circuit
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- Famous Physicists
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- Magnetic Fields
- Magnetic Flux Density
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- Newton’s Laws
- Operation of a Transformer
- Parallel Plate Capacitor
- Planetary Orbits
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- Fluids
- Absolute Pressure and Gauge Pressure
- Application of Bernoulli's Equation
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- Time Speed and Distance
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- Work Done
- Fundamentals of Physics
- Further Mechanics and Thermal Physics
- Bottle Rocket
- Charles law
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- Magnetic Flux
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- RL Circuit
- Measurements
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- Bulk Properties of Solids
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- Projectile Motion
- Scalar and Vector
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- Young's Modulus
- Medical Physics
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- Modern Physics
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- Phase Angle
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- Velocity
- Particle Model of Matter
- Physical Quantities and Units
- Converting Units
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- SI Prefixes
- Standard Form Physics
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- Use of SI Units
- Physics of Motion
- Acceleration
- Angular Acceleration
- Angular Displacement
- Angular Velocity
- Centrifugal Force
- Centripetal Force
- Displacement
- Equilibrium
- Forces of Nature Physics
- Galileo's Leaning Tower of Pisa Experiment
- Inclined Plane
- Inertia
- Mass in Physics
- Speed Physics
- Static Equilibrium
- Radiation
- Antiparticles
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- Atomic Model
- Classification of Particles
- Collisions of Electrons with Atoms
- Conservation Laws
- Electromagnetic Radiation and Quantum Phenomena
- Isotopes
- Neutron Number
- Particles
- Photons
- Protons
- Quark Physics
- Specific Charge
- The Photoelectric Effect
- Wave-Particle Duality
- Rotational Dynamics
- Angular Impulse
- Angular Kinematics
- Angular Motion and Linear Motion
- Connecting Linear and Rotational Motion
- Orbital Trajectory
- Rotational Equilibrium
- Rotational Inertia
- Satellite Orbits
- Third Law of Kepler
- Scientific Method Physics
- Data Collection
- Data Representation
- Drawing Conclusions
- Equations in Physics
- Uncertainties and Evaluations
- Space Physics
- Thermodynamics
- Heat Radiation
- Thermal Conductivity
- Thermal Efficiency
- Thermodynamic Diagram
- Thermodynamic Force
- Thermodynamic and Kinetic Control
- Torque and Rotational Motion
- Centripetal Acceleration and Centripetal Force
- Conservation of Angular Momentum
- Force and Torque
- Muscle Torque
- Newton's Second Law in Angular Form
- Simple Machines
- Unbalanced Torque
- Translational Dynamics
- Centripetal Force and Velocity
- Critical Speed
- Free Fall and Terminal Velocity
- Gravitational Acceleration
- Kinetic Friction
- Object in Equilibrium
- Orbital Period
- Resistive Force
- Spring Force
- Static Friction
- Turning Points in Physics
- Cathode Rays
- Discovery of the Electron
- Einstein's Theory of Special Relativity
- Electromagnetic Waves
- Electron Microscopes
- Electron Specific Charge
- Length Contraction
- Michelson-Morley Experiment
- Millikan's Experiment
- Newton's and Huygens' Theories of Light
- Photoelectricity
- Relativistic Mass and Energy
- Special Relativity
- Thermionic Electron Emission
- Time Dilation
- Wave Particle Duality of Light
- Waves Physics
- Acoustics
- Applications of Ultrasound
- Applications of Waves
- Diffraction
- Diffraction Gratings
- Doppler Effect in Light
- Earthquake Shock Waves
- Echolocation
- Image Formation by Lenses
- Interference
- Light
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- Ultrasound
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- X-rays
- Work Energy and Power
- Conservative Forces and Potential Energy
- Dissipative Force
- Energy Dissipation
- Energy in Pendulum
- Force and Potential Energy
- Force vs. Position Graph
- Orbiting Objects
- Potential Energy Graphs and Motion
- Spring Potential Energy
- Total Mechanical Energy
- Translational Kinetic Energy
- Work Energy Theorem
- Work and Kinetic Energy

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Jetzt kostenlos anmeldenIn Physics, prefixes are words placed before quantities to modify their meaning. For example, when we refer to ‘sub-zero temperatures’ on a snowy day, the prefix ‘sub’ meaning ‘lower than’, we are describing temperatures lower than zero. Other common prefixes are ‘mega’ and ‘giga’, which are used every day in computing.

SI units use prefixes to express especially large or small quantities. Using prefixes simplifies the expressions and standardises the terms used to describe numbers of any size.

The order of magnitude is a classification system based on the relative size of an object. In the SI system, we can say that an object is one order of magnitude larger than other objects if its measured value is ten times larger than the others. See the following examples:

A length of 20 metres is one order of magnitude larger than 1 metre, as 20 metres is more than ten times 1 metre.

How about kilograms? 10 grams is one order of magnitude larger than 1 gram, 100 grams is one order of magnitude larger than 10 grams, and 1 kilogram is one order of magnitude larger than 100 grams. There are, therefore, three orders of magnitude between the gram and the kilogram.

Symbols simplify the writing and calculation of mathematical equations and results. There is a symbol for every SI prefix.

Symbols as prefixes exist for large and small values, and every prefix and symbol represents an order of magnitude. A familiar example is cm, the centimetre symbol. Its name means a hundredth of the length of a metre. Its order of magnitude is -2 against the metre, and its representation is 0.01.

The SI prefix table below covers quantities that are larger than one unit.

Table 1. Prefixes symbols and orders of magnitude or large quantities. | ||||
---|---|---|---|---|

Prefix | Symbol | Order of magnitude | Representation | Name |

yotta | Y | 24 | 1,000,000,000,000,000,000,000,000 | Septillion |

zetta | Z | 21 | 1,000,000,000,000,000,000,000 | Sextillion |

exa | E | 18 | 1,000,000,000,000,000,000 | Quintillion |

peta | P | 15 | 1,000,000,000,000,000 | Quadrillion |

tera | T | 12 | 1,000,000,000,000 | Trillion |

giga | G | 9 | 1,000,000,000 | trillion |

mega | M | 6 | 1,000,000 | million |

kilo | k | 3 | 1,000 | Thousand |

hecto | H | 2 | 100 | Hundred |

deca | da | 1 | 10 | Ten |

The SI prefix table below covers quantities that are smaller than one unit.

Table 2. Prefixes symbols and orders of magnitude or large quantities. | ||||
---|---|---|---|---|

Prefix | Symbol | Order of magnitude | Representation | Name |

deci | d | -1 | 0.1 | tenth |

centi | c | -2 | 0.01 | hundredth |

milli | m | -3 | 0.001 | thousandth |

micro | μ | -6 | 0.000,001 | millionth |

nano | n | -9 | 0,000,000,001 | billionth |

pico | p | -12 | 0,000,000,000,001 | trillionth |

femto | f | -15 | 0,000,000,000,000,001 | quadrilionth |

atto | a | -18 | 0,000,000,000,000,000,001 | quintillonth |

zepto | z | -21 | 0,000,000,000,000,000,000,001 | sextillionth |

Here is a simple example that you might come across in the news:

You might read that there will be a new renewable power plant near your area, which, under normal conditions, will produce 300 MWh. But just how much is that?

The symbol MWh stands for megawatts per hour. M is the symbol for Mega, meaning one million. 300 MWh, therefore, are 300,000,000 watts per hour. An average light bulb, by contrast, consumes about 30 watts per hour. If you divide the power produced by the new power plant by the amount of energy consumed by the light bulb, it becomes clear that the plant will provide enough energy for 10,000,000 light bulbs per hour.

In the SI units, a prefix is applied when a quantity is smaller or larger than the original unit by a factor of ten. Every prefix in the SI system tells us that a quantity is one order of magnitude smaller or larger than the previous one. See the following examples:

Temperature: 3 megakelvin, mega meaning 1 million. This measurement is six orders of magnitude larger than any temperature in the range of 1 to 9 kelvin.

Length: 4.5 kilometres, kilo meaning 1000. This measurement is three orders of magnitude larger than any measurement in the range of 1 to 9 metres.

We can also use calculations to know how many orders of magnitude some object is different to another one if we know their size. Orders of magnitude can tell us how the size of an object compares to others. This method of comparison is useful when measuring lengths or areas and approximating the results to know how accurate a measurement is. See the following example of using this approach:

A bolt used to manufacture a machine must have a width of 3 cm but can be slightly larger or smaller by 0.03 cm. If the bolt is wider than 3cm + 0.03 cm, it will not fit, and if it is smaller than 3 cm-0.03 cm, it will not be tight enough.

You can determine the relative size of the deviation allowed in the measurement by making a simple division:

\(\text{relative size} = \frac{3 \space cm}{0.03 \space cm} = 50\)

This indicates that the bolt size is 50 times larger than the deviation allowed in the bolt width. The allowed deviation, therefore, is two orders of magnitude lower than the width of the bolt. When making measurements to produce objects, two, three or even four to five orders of magnitude smaller mean more accurate pieces.

- Prefixes allow us to use short, standardised names for very large and very small quantities.
- Prefixes have a symbol associated with them.
- The SI symbols have the same meaning as prefixes.
- We find quantity symbols in every discipline, from natural sciences to the arts.
- The order of magnitude helps us to know how large or small an object is compared to others.

SI prefixes are words used to substitute names of large or small quantities.

A list of useful prefixes for measurements larger than the unit and their values are: yotta (10^24), zetta (10^21), exa (10^18), peta (10^15), tera (10^12), giga (10^9), mega (10^6), kilo (10^3), hecto (10^2), and deka (10).

A list of useful prefixes for measurements smaller than the unit and their values are: yocto (10^-24), zepto (10^-21), atto (10^-18), femto (10^-15), pico (10^-12), nano (10^-9), micro (10^-6), milli (10^-3), centi (10^-2), and deci (10^-1).

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