Appendix 8 Weights and Measures

Metric

GB and US

length

10 millimetres (mm)

= 1 centimetre (cm)

= 0.3937 inches (in)

100 centimetres

= 1 metre (m)

= 39.37 inches or 1.094 yards (yd)

1000 metres

= 1 kilometre (km)

= 0.62137 miles or about 5/8 mile

surface

100 square metres (m²)

= 1 are (a)

= 0.0247 acres

100 acres

= 1 hectare (ha)

= 2.471 acres

100 hectares

= 1 square kilometre (km²)

= 0.386 square miles

weight

10 milligrams (mg)

= 1 centigram (cg)

= 0.1 543 grains

100 centigrams

= 1 gram (g)

= 15.4323 grains

1000 grams

= 1 kilogram (kg)

= 2.2046 pounds

1000 kilograms

= 1 tonne

= 19.684 cwt

capacity

1000 millilitres (ml)

= 1 litre (1)

= 1.75 pints or 2.101 US pints

10 litres

= 1 decalitre (dl)

= 2. 1997 gallons or 2.63 US gallons

QUANTITY

SYMBOL

SI UNIT

SYMBOL

DERIVATION

acceleration

a

m s ^-2

–

velocity/time

acceleration due to gravity

g

m s^-2

–

velocity/time

amount of substance

n

mole

mol

mole fraction (n) used

amplification factor

μ

a ratio

–

–

angle

θ_pφ_pα₁

–

–

–

– of incidence

i

degree or radian

°

–

– of refraction

r

degree or radian

°

–

– Bragg

θ

number

–

–

– critical

с

degree or radian

°

–

anode slope resistance

R_A

ohm

Ω

ДV_a/ДV_a

area

A

metres square

m²

l x b

atomic number

Z

a number

–

number of protons

Avogadro constant

L, N_A

number

–

–

breadth

b

metre

m

fundamental unit

capacitance

С

farad

F

charge/p.d.

charge, electric

Q

coulomb

С

current x time

on electron

e

coulomb

С

l.6 x 10^-19C

conductance

G

ohm^-1

Ω^-1

reciprocal of resistance

current, electric

I

ampere

A

fundamental unit

decay constant

λ

a ratio

–

–

density

ρ

kg m^-3

–

m/V

distance along path

s

metre

m

fundamental unit

efficiency

η

a ratio

–

work output/ work input

electrochemical equivalent

z

gC^-1

–

mass/charge

electromotive force

E

volt

V

energy/charge

electron

e

energy

E

joule

J

N m

– kinetic

E_k

joule

J

N m.E_k=Smv²

– potential

E_p

joule

J

N m.E_p=mgh

Faraday constant

F

coulomb mol^-1

C mol^-1

96 500 С mol^-1

field strength,

E

Vm^-1

–

potential gradient:

electric

p.d./dist.

magnetic

H

ampereturns

–

current no. of turns

flux, magnetic

Ф

weber

Wb

e.m.f./rate of change of flux

flux density

В

tesla

Т

flux/area

focal length

f

metre

M

–

force

F

newton

N

kg m s^-2

free energy

ΔG

joule

J

frequency

f

hertz

Hz

oscillations/ time

gas constant

r

joule

J

energy

half-life, radioactivity

t_1/2

second

s

fundamental unit

heat capacity

С

JK^-1

–

quantity of heat/ temp. rise

heat of reaction

ΔH

joule

J

heat energy

heat capacity, specific

с

J K^-1kg^-1

–

heat capacity/ mass

heat, quantity of

q

joule

J

energy

height

h

metre

m

fundamental unit

image distance

v

metre

m

fundamental unit

inductance, mutual

M

henry

H

induced e.m.f./rate of change of current

self

L

henry

H

–

intensity of radiation

I

a number

–

–

latent heat

L

joule

J

quantity of heat

–, specific

l

J kg^-1

–

quantity of heat

–, molar

L_m

joule mol^-1

J

quantity of heat

length

l

metre

m

fundamental unit

magnetizing force

H

ampereturns

–

–

magnetic moment

m

Wb m

–

torque in unit magnetic field

magnification, linear

m

a ratio

–

–

mass

m

kilogramme

kg

fundamental unit

– number

A

a number

–

number of neutrons + protons

molar volume

V_m

(dm³)

–

volume of 1 mole

molar solution

M

a ratio

moles/dm³

moment of force

–

N m

–

force perp. distance

neutron number

N

a number

–

number of neutrons

number

n

–

–

–

– of molecules

N

–

–

–

– of turns on coil

n

a number

–

–

– order of spectrum

p

a number

–

–

object distance

u

metre

m

fundamental unit

peak current

I₀

ampere

A

see current

peak e.m.f.

E₀

volt

V

see e.m.f.

period

Т

second

s

fundamental unit

permeability

μ

H m^-1

–

henry/metre

– of vacuum

μ₀

H m^-1

–

–

–, relative

μ_r

a ratio

–

м = м / м₀

permittivity

ε

F m^-1

–

farad/metre

– of vacuum

ε₀

F m^-1

–

farad/metre

–, relative

ε_r

a ratio

–

е_r = е /е₀

potential, electric

V

volt

V

energy/charge

potential difference

V

volt

V

energy/charge

power

P

watt

W

J s^-1

pressure

p

pascal

Pa

Nm^-2: force/area

radius

r

metre

m

fundamental unit

reactance

X

ohm

Ω

E₀ /l₀

refractive index

n

a ratio

–

–

resistance

R

ohm

Ω

p.d./current

resistivity, electrical

ρ

ohm-metre

resistance x length

relative density

d

a ratio

–

с_sub / с_water

r.m.s. current

I_rms

ampere

A

see current

r.m.s. voltage

V_rms

volt

V

see e.m.f.

slit separation

S

metre

m

fundamental unit

tension

Т

newton

N

see force

temperature, Celsius

θ

degree С

°C

from kelvin

temp., interval

θ

degree

° or K

–

temp., absolute

T

kelvin

К

fundamental unit

thickness

d

metre

m

fundamental unit

time

t

second

s

fundamental unit

torque

T

N m

–

see moment

turns ratio

Т

a ratio

–

n_sec / n_prim

(unit of electricity)

–

kWh

–

kilowatt hour

velocity

u, v

m s^-1

–

distance/time

– , angular

ω

second ^-1

s^-1

angle/time

– of e.m. waves

c

m s^-1

–

–

– of sound

m s^-1

–

–

volume

V

metre cubed

m³

l b h

wavelength

λ

metre

m

fundamental unit

work

w

joule

J

force x distance

(N • m)

weight

W

newton

N

kg m s^-2 or mg