Use of SI units and their prefixes Flashcards – AQA A-level Physics (7408)

What are SI base units?

Fundamental units from which other SI units are constructed.

What is the SI base unit of mass? Give its name and symbol.

Kilogram ($\mathrm{kg}$).

What is the SI base unit of length? Give its name and symbol.

Metre ($\mathrm{m}$).

What is the SI base unit of time? Give its name and symbol.

Second ($\mathrm{s}$).

What is the SI base unit of amount of substance? Give its name and symbol.

Mole ($\mathrm{mol}$).

What is the SI base unit of temperature? Give its name and symbol.

Kelvin ($\mathrm{K}$).

What is the SI base unit of electric current? Give its name and symbol.

Ampere ($\mathrm{A}$).

What two parts are used to express a quantity?

A numerical value and a unit.

What rule about letter case applies to unit symbols?

Unit symbols are case-sensitive.

What is an SI derived unit?

A unit formed by multiplying, dividing or raising SI base units to powers. It expresses a quantity related to base quantities.

How is the joule ($\mathrm{J}$), an SI unit of energy, expressed in SI base units?

$\mathrm{kg\,m^2\,s^{-2}}$

What does an SI prefix attached to a unit denote?

A power-of-ten multiple or submultiple of the unit.

What are the symbol and factor for the SI prefix tera?

T; $10^{12}$

What are the symbol and factor for the SI prefix giga?

G; $10^9$

What are the symbol and factor for the SI prefix mega?

M; $10^6$

What are the symbol and factor for the SI prefix kilo?

k; $10^3$

What are the symbol and factor for the SI prefix centi?

c; $10^{-2}$

What are the symbol and factor for the SI prefix milli?

m; $10^{-3}$

What are the symbol and factor for the SI prefix micro?

μ; $10^{-6}$

What are the symbol and factor for the SI prefix nano?

n; $10^{-9}$

What are the symbol and factor for the SI prefix pico?

p; $10^{-12}$

What are the symbol and factor for the SI prefix femto?

f; $10^{-15}$

How does letter case affect SI prefix symbols?

Prefix symbols are case-sensitive.

How is a nonzero number written in standard form, and what are the restrictions on its parts?

$a\times10^n$, where $1\leq |a|<10$ and $n$ is an integer.

What remains unchanged when a measurement is converted to a different unit?

The quantity measured.

How is a measurement converted from one unit to another?

Multiply its numerical value by a factor based on the relationship between the units, chosen to replace the original unit with the required unit.

How does the size of a unit affect the numerical value of a fixed quantity?

A smaller unit gives a larger numerical value; a larger unit gives a smaller numerical value.

How is a unit conversion factor applied when the unit is raised to a power?

Raise the conversion factor to the same power.

How many joules are in one electronvolt?

$1\,\mathrm{eV} = 1.602176634\times10^{-19}\,\mathrm{J}$

How many joules are in one kilowatt-hour?

$1\,\mathrm{kW\,h} = 3.6\times10^6\,\mathrm{J}$

Is a kilowatt-hour a unit of energy or power?

Energy, not power.