Notebook of Gerard Henderson Cowan - Part 8

Elementary Electricity
Electricity is the name
given to that which causes all
electric phenomina.

It is in everything but is in a 

dormant state and needs some

contrivance to make it flow.

It has to be kept in a certain

channels.

Certain substances allow the

flow of Electricity these

are called conductors, others

will not allow the flow

of electricity or at least would

need a very high pressure to

drive it through them,

these are called nonconductors

or insulators.

The following are a few

conductors I The Earth, II Water

(the muddier the better) III All metals

Non Conductors, I Air.  II Rubber
 

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Non Conductors Contd

III   Ebonite  IV  Glass  V  China  VI  Wood

Silver is the best known

conductor but owing to its high

value is seldom used.

Next is copper which is used

extensively but for army

work it is too soft and

will not stand the rough

usuage.

Stel , Steel, though not by any 

means the next best conductor

is sufficient and is almost

exclusively used in Army

Work.

Circuit

Electricity must have a complete

path through which to flow

this is called the circuit

Cell

Some contrivance is needed

to make the electricity flow

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this contrivance in the

case of telephones usually

takes the form of a Cell

or a number of cells (Battery)

Key or Switch

Electricity is controlled,

so it can be used at will,

by a key, This simply makes

a break in the circuit thus

interrupting the flow of

electricity.

Direction of flow

It is not known in which

direction electricity flows

although it is known it does

flow, but it is assumed

that it flows from the

positive terminal of a cell to

the negative terminal

If more than one channel is open to it

it will flow equally through

Circuits

A Hand drawn diagram

B Hand drawn diagram

C Hand drawn diagram

ELECTRICITY, if more than

one path is provided for it,

will divide and an equal 

amount will flow along

each path or wire provided

they are of equal thickness

 

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through each provided the

wires are of equal thickness.

You could have any number

of channels and the electricity

would divided up and

flow equally through each.

This would give less resistance

than forcing the same amount

of current through the one

channel. The thicker the

wire the less resistance

and vice versa.

If a bare circuit was laid

on the earth electricity would

not flow or would not keep

to the circuit as the earth

is a good conductor

therefore it has to be

confined to its circuit

by an insulator, generally

paper or rubber.

Magnetic effect caused by passing

electricity along a wire

Hand drawn diagram MAGNETIC EFFECT OR FLUX Caused by current passing along wire

Method of Connecting Cells Hand drawn diagram Total voltage in circuit 4.5

Cells connected in series Hand drawn diagram Total voltage in circuit 1.5

Cells connected in parallel Hand drawn diagram Cells in series  Cells in parallel

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Wasting

A certain amount of electricity

is eaten up in forcing the

current through the resistance

of the circuit. Thus if the

circuit is large several cells,

forming a battery may be

needed.

Heating

Electricity has a heating effect

and a large current will make a small

wire very hot

Magnetic Effect

This is a very important effect

it has on the wire it always

acts in circles around the wire

Joining broken circuits

Never join two thick wires that

are broken by a thin one as

the resistance of the whole circuit

is thus reduced to the resistance

of the thin wire.

Hand drawn diagram-see original

 

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To flow electricity must have

a complete unbroken path of

conductors and at some part

of this circuit must have a

pontential difference, this difference

of power causes an E.M.F. or

electric motive force.

The instrument which supplies

this difference in power is the 

cell. Types of cell commonly

used are the S. Cell and X. Cell.

The S. type Cell

This is an Army type. It is

composed of an a zinc case

(see diagram) covered with paraffined

waxed paper to insulate it.

Inside this zinc pot are

two strips of Sal-ammoniac

one down each side these

are insulated from the

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bottom of the case.

A rod of Carbon goes down the

centre and between this

rod and the Sal-ammoniac

is a canvass bag containing

magnese dioxide. Above this

again is compressed sawdust

to prevent any moisture

getting at the cell, On top

of this sawdust is more

insulating material, generally

bitumen.

Two glass tubes protrude down

through the sawdust and bitumen

to the manganese dioxide. One

of these is corked this one is used

to put water into the cell, the

other is for the escape of gass

This cell has two terminals

T the positive terminal attached

to the carbon rod and negative

attached to the zinc case.

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This cell is not ready for use when

issued. To make active, remove

the cork from the glass tube

and fill with water, do this

every 10 minutes until the

cell is thoroughly soaked

then leave it to stand in an

upright position for eight hours

after that time has elapsed shake

out any surplus water and 

the cell is ready for use.

Action of the Cell

The water mixing with the Sal-ammoniac

makes a solution

This solution attacks the zinc

XXXX setting up an a violent

agitation of electricity, this

electricity tend to flow

towards the carbon and

when the circuit is complete

flows out through the Carbon

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round the Circuit and back through

the zinc.

There is also another action

that takes place. The Solution

acting on the water takes

all the oxygen leaving only

hydrogen gas this attaches

itself to the carbon rod thus

preventing the flow of electricity

It also sets up an electrical

pressure in the carbon which

acts against that of the zinc

The maganese dioxide is used

to vaporise the hydrogen

which passes out through 

the gass vent.

Magnetism

Is that which has the power

of attracting iron or other

magnetic substances

Magnets

There are two distinct classes

I Permenant magnets

which retain their magnetism

for an more or less permanently

II  Electro magnets

which are not magnets except

when there is a flow of electric

electricity around it.

Polarity

Magnets have a polarity of their

own, one end id north seeking

the other is south seeking.

Magnetic Flux

There is a strong force acting

around magnets all the time

this is known as the magnetic

field the lines of force in this