Derived Units in SI Measurements

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Questions and Answers

What is the current definition of a meter based on?

The average length of a day

The distance traveled by light in a vacuum in 1/299792458 of a second (correct)

The length of the Earth’s equator

The distance between the North Pole and the equator

Which statement is true about the kilogram's current definition?

It relies on Planck’s constant and is expressed in the units of kg m² s⁻¹. (correct)

It is based on the mass of one liter of water at boiling point.

It is defined using the speed of sound in water.

It was initially equivalent to one cubic meter of mercury.

What fixed value is essential in the definition of the ampere?

The current through a resistor

The charge of the electron (correct)

The charge of a proton

The voltage measured across a capacitor

The kelvin scale is related to which constant for its definition?

Boltzmann constant Signup and view all the answers

What was the original definition of the second based on?

1/86400 of a solar day Signup and view all the answers

What is the symbol for the derived unit of electrical resistance?

Ω Signup and view all the answers

Which of the following derived units is associated with luminous flux?

lm Signup and view all the answers

How many derived units with special names are there?

22 Signup and view all the answers

What derived unit measures energy?

J Signup and view all the answers

Which of the following is NOT a dimensionless derived unit?

newton Signup and view all the answers

What is the derived unit for electric charge?

C Signup and view all the answers

Which derived unit expresses pressure?

Pa Signup and view all the answers

What derived unit is used to measure frequency?

Hz Signup and view all the answers

What is the symbol for liter?

l Signup and view all the answers

Which of the following is not a permitted non-SI unit?

bar Signup and view all the answers

What quantity does the symbol 'ha' represent?

area Signup and view all the answers

Which of the following non-SI units is used to measure energy?

electronvolt Signup and view all the answers

Which two symbols both represent logarithmic ratios?

Np and dB Signup and view all the answers

What is the quantity associated with the symbol 't'?

mass Signup and view all the answers

Which of the following units represents a plane angle?

° Signup and view all the answers

What unit has an alternative name of 'l' and measures volume?

liter Signup and view all the answers

Which unit for length is no longer permitted in the latest SI brochure?

angstrom Signup and view all the answers

What does the symbol 'au' stand for?

length Signup and view all the answers

What is the symbol for the unit of mass in the SI base units?

kg Signup and view all the answers

Which base unit is used to measure thermodynamic temperature?

K Signup and view all the answers

What property is the second defined based on?

Atomic clock Signup and view all the answers

Which of the following base units measures luminous intensity?

cd Signup and view all the answers

How are the names of the SI base units typically written?

In lowercase letters Signup and view all the answers

Why were the SI base unit definitions re-defined in 2019?

To derive from constant properties of nature Signup and view all the answers

What does the SI unit 'A' stand for?

Ampere Signup and view all the answers

Which unit is used to measure the amount of substance?

mol Signup and view all the answers

What is the symbol for the base unit of length?

m Signup and view all the answers

Which of the following is NOT one of the seven SI base units?

Energy Signup and view all the answers

What is the unit of density?

kg/m3 Signup and view all the answers

Which quantity is represented by the symbol 'V'?

Volume Signup and view all the answers

What does the abbreviation 'm/s' represent?

Meters per second Signup and view all the answers

What is the derived unit for acceleration?

meters per second per second Signup and view all the answers

Which symbol is used for concentration (molarity)?

C Signup and view all the answers

What defines a derived unit?

A unit created from two or more base units Signup and view all the answers

What is the SI unit for angular velocity?

radians/second Signup and view all the answers

Which of the following represents current density?

A/m2 Signup and view all the answers

What represents the unit for wave number?

m-1 Signup and view all the answers

How can a new derived unit be officially recognized?

By approval from the General Conference on Weights and Measures Signup and view all the answers

Study Notes

Derived Units

Derived units are combinations of base units
Written using lowercase letters
Some have special names
Symbols for named units start with a capital letter

Examples of Derived Units

Watt (W)
Hertz (Hz)
Coulomb (C)

SI Base Units

Time (second, s)
Length (meter, m)
Mass (kilogram, kg)
Electric Current (ampere, A)
Temperature (kelvin, K)
Amount of substance (mole, mol)
Luminous intensity (candela, cd)

More Derived Units

Area (square meter, m²)
Volume (cubic meter, m³)
Density (kilograms per cubic meter, kg/m³)
Speed (meters per second, m/s)
Acceleration (meters per second squared, m/s²)
Pressure (pascal, Pa)
Force (newton, N)
Energy (joule, J)
Frequency (hertz, Hz)
Power (watt, W)
Voltage (volt, V)
Charge (coulomb, C)

Additional Points

There are 22 derived units with special names
There are more than 100 other derived units, expressed using base units
Several SI units that were in the 8th brochure are not in the 9th: bar, mmHg, ångström, gauss
Derived units may be based on physical constants
The definitions of the SI base units are based on natural phenomena, not physical objects.

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Description

This quiz covers derived units in the International System of Units (SI), including their definitions and examples. You'll learn about the relationships between base units and derived units, such as watt, coulomb, and more. Test your knowledge of how these units are used in scientific contexts.