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27 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

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James

Prescott

Joule

(
24

December

1818



11

October

1889
)

was

an

English

physicist,

born

in

Salford
,

Lanashire
,

England
.

He

came

from

a

wealthy

family

who

was

involved

in

the

brewing

industry
.

As

a

child,

James

was

weak

and

shy,

and

suffered

from

a

spinal

disorder
.

Because

of

these

limitations,

he

preferred

studies

to

physical

activity
.




He

was

educated

at

home

by

private

tutors

until

the

age

of

fifteen
.

He

then

went

to

work

in

the

family

brewery

as

his

father

became

ill
.

However,

he

and

his

older

brother

continued

their

education

part
-
time

with

private

tutors

in

Manchester
.

They

were

taught

chemistry,

physics,

the

scientific

method,

and

mathematics

by

the

famous

scientist

John

Dalton
.




Although

he

only

received

two

years

of

education

from

John

Dalton,

these

teachings

were

what

made

him

one

of

the

most

exact

measurement

takers

of

his

day
.

It

made

him

form

a

desire

to

increase

his

knowledge

by

original

researches
.






John Dalton


His

great

desire

was

to

continue

to

study

science,

so

he

set

up

a

laboratory

in

his

home

and

began

to

study

electric

motors

and

experimenting

before

and

after

work

each

day
.

His

brewing

hobby

also

becomes

his

first

time

to

use

physics
.

Making

all

of

his

machines

and

devices

more

efficient

is

where

his

skills

for

physics

came

to

shine
.

In

doing

this

his

studies

with

energy

began
.


Joule

had

the

idea

that

he

could

use

the

electric

motor

to

convert

the

family

brewery

from

steam

power

to

electric

power
.

He

spent

a

great

deal

of

his

life

in

determining

the

mechanical

equivalent

of

heat,

inspired

from

his

bel ief

that

heat

was

derived

from

work
.

By

the

1840
s,

scientists

had

real ized

that

heat,

electricity,

magnetism,

chemical

change

and

the

energy

of

motion

were

all

inter
-

convertible
.

Joule

was

extremely

involved

with

this

work,

and

between

1837

and

1847
,

he

established

the

principle

of

conservation

of

energy,

and

the

equivalence

of

heat

and

other

forms

of

energy
.

He

was

fascinated

by

the

possibil ity

that

electromagnets

might

become

useful

as

sources

of

industrial

power
.

He

began

to

link

together

electricity,

heat

and

mechanical

power

by

observing

the

transformations

they

went

through
.

By

1840

he

establ ished

that

the

amount

of

heat

produced

per

second

in

a

wire

carrying

an

electric

current

equals

the

current

(I)

squared

multipl ied

by

the

resistance

(R)

of

the

wire
.

The

heat

produced

is

the

electric

power

lost

(P)
.

(That

is,

P=I
2
R
.
),

which

is

Joule's

Law
.








Still

with

the

idea

that

it

was

possible

to

convert

mechanical

work

directly

into

heat

without

any

electrical

steps,

Joule

experimented

from

1842

to

1878

on

such

conversions
.

Around

1845
,

he

was

able

to

demonstrate

in

a

paddle
-
wheel

experiment,

which

involved

the

shaft

and

paddles

being

driven

by

a

falling

weight

suspended

from

a

pulley,

that

the

same

amount

of

work,

however

done,

always

produced

the

same

amount

of

heat
.

This

enabled

Joule

to

conclude

that

heat

was

a

form

of

energy
.

The

mechanical

equivalent

of

heat

is

a

constant

and

is

designated

by

the

symbol

J

in

honour

of

James

Joule
.




Joule

displayed

an

amazing

clarity

in

conceiving,

executing,

describing

and

explaining

his

experiments
.

Joule’s

work

on

the

relationship

of

heat,

electricity

and

mechanical

work

was

largely

ignored

until

1847
.

While

Joule

was

not

the

first

scientist

to

suggest

this

principle,

he

was

the

first

to

demonstrate

its

validity
.

He

showed

that

“work

can

be

converted

into

heat

with

a

fixed

ratio

of

one

to

the

other,

and

that

heat

can

be

converted

into

work
.


Joule’s

principle

of

energy

conservation

formed

the

basis

of

the

first

law

of

thermodynamics
.

This

law

states

that

energy

can

neither

be

created

nor

destroyed,

but

it

can

be

changed

from

one

form

into

another
.




James

Prescott

Joules

was

a

determined

scientist

who

never

gave

up

on

his

research

or

experiments

to

prove

his

theories
.

Although

his

papers

were

responded

by

the

Royal

Society

and

the

journalists

unenthusiastically,

he

patiently

persisted

until

1847
,

when

William

Thomson

finally

took

notice

of

his

work

on

the

relationship

of

heat,

electricity

and

mechanical

work
.




Other

than

that,

he

was

very

humble

about

his

discoveries

as

he

cared

more

about

the

results

of

his

experiments

than

his

recognition

for

them
.

Most

importantly,

he

was

committed

to

his

research

to

prove

his

theories

and

never

gave

up

on

his

work
.




All of these values definitely have inspired us to
continue

learning Science, to be scientists and
maybe one day, we can discover and
develop a theory and contribute it back to the
scientific world and impart knowledge to
others and benefit them.



We

have

learnt

more

about

James

Prescott

Joule,

one

of

the

greatest

scientists

in

the

world,

about

his

beneficial

discoveries

and

know

how

important

Science

is

and

how

it

can

improve

our

lives
.

We

have

learnt

that

perseverance

and

determination

are

the

keys

to

becoming

a

great

scientist,

and

at

the

same

time,

be

humble

about

our

discoveries
.




However,

as

physics

is

an

area

consisting

of

many

different

topics,

we

were

confused

at

times

whether

his

major

contribution

was

electricity

or

heat
.

In

the

end,

we

did

more

research

and

found

out

more

about

his

contributions,

which

were

mostly

heat
.




http
:
//en
.
wikipedia
.
org/wiki/James_Prescott_Joule


http
:
//simple
.
wikipedia
.
org/wiki/James_Prescott_Joule


http
:
//www
.
zephyrus
.
co
.
uk/jamesjoule
.
html


http
:
//www
.
answersingenesis
.
org/articles/cm/v
15
/n
2
/james
-
joule


https
:
//thescienceclassroom
.
wikispaces
.
com/James+Prescott
+Joule


http
:
//www
.
google
.
com
.
sg


Done by:

Liaw

Wan Qing (6),

Lorraine Lim
Wen

Jing (
8
),

Wee Yu
Xuan

(21)