Number and
Type of location Number and
bell or of bells Type of location
Job buzzer and buzzers control of controls
---------------------------------------------------------------------
Summon others In the house-- Enough to Push- One at the
to the small to cover all buttons telephone
telephone medium buzzers usual work and each
In locations extension
outbuildings-- phone
medium to
large bells
Outdoors--
large
weatherproof
bell
All transformer-
powered
---------------------------------------------------------------------
Notify club Medium to large One may be Hose One--in
member that bell-- enough--if diaphragm the
car is at his transformer- mounted on driveway
produce stand powered the back of -----------------------
the stand (Complete driveway
including control,
are available,
ready to plug in.)
--------------------------------------------------------------------
Warn of power Battery-powered One near Relay, One, at
failure to buzzer, medium the held open main
incubator or size poultryman's as long as switch of
brooder bedroom power is on, hatchery
closed by or
spring if brooder
interruption house
occurs
--------------------------------------------------------------------
Warn of Battery-powered One, in or Temperature One, with
dangerously buzzer, medium near the detector bulb
warm size kitchen (sensitive inside
temperature thermostat) freezer
in freezer
---------------------------------------------------------------------
How to Plan Your System
To save your time and steps when the telephone rings for someone else in
your family who is some distance away, you can install a simple bell or
buzzer system to summon that person.
First, you must plan what you are going to do. On a large sheet of
paper, draw to scale (roughly) a plan of your house and grounds,
including those places where phones are located. It will help if you
rule off your paper in 1/8" or 1/4" squares and let each square equal
one foot. Show the location of poles supporting your wiring.
Next, pick out those areas where you or others would likely be when
someone else would answer the phone and want to call you to it.
After you have thought about this, and talked it over with members of
your family, show locations on your plan where you think you would like
to have buzzers or bells, and show a button beside each telephone.
(Generally, you should have a bell or buzzer near each phone, also.)
Figure 3 shows diagrams of various types of systems, and will help you
determine the number of wires you will have to install to connect the
buttons and bells that you have planned.
Inside, you will connect your transformer and the various buttons and
bells with ordinary indoor bell wire. Outdoors, however, you should use
weatherproof 2-wire or 3-wire telephone twist.
Show on your plan the distances that must be traversed by each type of
wire, and show the number of conductors in each. Don't overlook the
vertical distances (one floor to another).
[Illustration: Figure 3]
Materials You'll Need
Because no two situations are just alike, it will be necessary for you
to make your own list of materials.
As a guide, however, here is a list of typical materials, with the
quantities left blank, for you to fill in as your own requirements and
measurements dictate.
10-volt transformer
--- Door buzzers
--- Doorbells
--- Weatherproof outdoor type bells
--- ft. indoor bell wire
--- ft. 2-wire weatherproof telephone twist
--- ft. 3-wire weatherproof telephone twist
--- lbs. staples (insulated)
--- entrance insulators (for attaching
weatherproof to buildings and poles)
Because your transformer must be wired into your regular house current,
you should have some help on this from an electrician or other qualified
person. Also, you should get that person to review your plans and
materials list before you place an order.
Install According to Your Plan
With the aid of an electrician or other qualified person, install your
transformer, and test it.
You may then go ahead and complete your signal system, checking
carefully with your plan, and making sure that your installations are
both electrically and mechanically secure.
Test your system in all possible ways that it might be used.
Demonstrations You Can Give
Build a demonstration board incorporating a farm or home layout, with
pushbuttons or other controls and bells and buzzers appropriately
located. Show and tell how the system would save time and energy.
Show and tell how some of these work, and their value: power-off alarm,
freezer alarm, fire alarm, driveway alarm.
For More Information
Ask your power supplier or your nearest electrical supply house for
catalogs or literature on various types of signal systems, or ask a
dealer to show you equipment he has in stock.
LESSON NO. B-11
Credit Points 2
FIRST AID FOR ELECTRICAL INJURIES
What would you do if you saw someone who had been hurt by electricity?
Did you know that you could save his life, if you had taken the time to
learn and practice a few simple rules of electrical first aid?
First aid training equips you to know what to do and what not to do for
the injured until medical help can be obtained. While the main benefits
are for you and your family, no one can call himself a good citizen if
he fails to help a stranger who has been hurt.
The information given here is only for electrical injuries. Perhaps what
you learn will inspire you to take a complete course in first aid.
What to Do
Learn how to prevent electrical accidents, and what to do if an
electrical accident occurs.
1. Make an electrical hazard hunt in your home or on your farm. Point
out to your parents everything that should be repaired or replaced for
safety's sake.
2. Read the first aid suggestions that follow. Learn them.
3. Get to know the six steps that are outlined for mouth-to-mouth rescue
breathing. Practice them on your brother, sister, or parents. Teach the
entire family how to do it.
Electricity Can Kill
In this day of hundreds of uses of electricity, you should know about
electrical dangers. Electrocution can occur from either low voltage
(household type) or high voltage currents. Sometimes household voltages
are more hazardous because people underestimate the dangers involved.
A fraction of an ampere passing through your heart muscles can be fatal.
Your body offers some resistance to the flow of electricity to ground.
If you are standing on wet ground or in water, or if your skin is damp,
this resistance is greatly reduced.
Wire cables within walls and cords on appliances are all insulated with
a shock proof covering. Continued use, age, or damage may expose a bare
wire and create a hazard. The point of exposure need be only a fraction
of an inch. Cords are often used and abused. Exposed wires and signs of
wear are danger signals.
Always be wary of overhead wires. People have been injured or killed
when kite strings, model plane control lines, irrigation pipe, and water
well equipment have come in contact with the power supplier's or their
own overhead wiring.
Prevent Accidents
Underwriters' Laboratories (UL) have taken steps to see that minimum
safety standards are met in the manufacture of electrical equipment.
Look for the UL label when you buy cords or appliances. Never place
cords under carpets or furniture, or drape them over a nail. Replace or
repair worn cords without delay.
Be especially careful when operating electric devices in the bathroom.
Keep in mind the dangers of a wet floor, grounded metal pipes, and wet
skin. Turning on an AC radio while you are taking a bath is asking for
real trouble.
There may be shorts in electric devices. Keep your hands dry when using
them, and do not touch them along with grounded metal objects. If you
ever get a slight shock, sound the danger signal and do something about
it.
Think, Then Act
Your first thought in rescuing a victim from an electrical accident
should be your own safety. Speed is also important, because a few
seconds or minutes may save a life.
The first question you should ask yourself is "Can I quickly turn off
the power?" This would be easier to do in the home than outside. In the
case of a victim trapped in a bathtub from a radio accidentally knocked
into the water, it might mean simply removing the plug from the wall
outlet. If a victim is found grasping shorted, permanently installed
equipment and cannot let go, the main switch might be used for quick
release of the current.
Outdoors, especially with high tension wires, your danger in rescue is
much greater. To handle the victim, touch him only with a long dry
stick, dry rope, or a long length of dry cloth. Be sure your hands are
dry and that you are standing on a dry board. A broom might be a good
lever to pry a victim from a high tension wire but never use a green
stick containing sap.
First Aid
Once the rescue has been made and the victim is free of further danger,
check to see if breathing has stopped. If so, start artificial
respiration _immediately_ and send someone for a doctor.
Artificial respiration must be started as soon as possible after normal
breathing ceases. _Most persons will die within 6 minutes or less if
breathing stops completely unless they are given artificial
respiration._ Precious minutes may have passed before you get to the
victim. Since the victim may be within seconds of death by the time you
are able to touch his body, you should seek to obtain an air flow to and
from the lungs _immediately_.
The victim may seem stiff as an effect of the current, so don't give up
easily. Continue the procedure for several hours. If transportation is
necessary, remember that there may be internal injury, fractures, or
severe burns.
Mouth-To-Mouth Rescue Breathing
There are various effective ways to give artificial respiration, each
with its advantages and disadvantages. The mouth-to-mouth method is
recommended as a good one to master. It can be used on victims of
drowning, suffocation, and asphyxiation, too. People have been known to
save lives with less exposure to the correct procedure than you are
getting by reading this. So, pay attention and remember what you read.
Step 1. Turn the victim on his back. Wipe out victim's mouth quickly.
Turn his head to the side. Use your fingers to get rid of mucus, food,
sand, and other matter.
[Illustration: Head Position]
Step 2. Straighten victim's head and tilt back so that chin points up.
Push or pull his jaw up into jutting out position to keep his tongue
from blocking air passage. This position is essential for keeping the
air passage open throughout the procedure.
[Illustration: Push Jaw Up]
[Illustration: Pinch Nostrils]
Step 3. Take a deep breath, place your mouth tightly over victim's
mouth, and pinch nostrils closed to prevent air leakage. For a baby,
cover both nose and mouth tightly with your mouth. (Breathing through
handkerchief or cloth placed over victim's mouth or nose will not
greatly affect the exchange of air.)
[Illustration: Breathe]
Step 4. Breathe into victim's mouth or nose until you see his chest
rise. (Air may be blown through victim's teeth, even though they may be
clenched.)
Step 5. Remove your mouth and listen for the sound of returning air. If
there is no air exchange, recheck jaw and head position. If you still do
not get air exchange, turn victim on side and slap him on back between
shoulder blades to dislodge matter that may be in throat. Again, wipe
his mouth to remove foreign matter.
Step 6. Repeat breathing, removing mouth each time to allow air to
escape. For an adult, breathe about 12 times per minute. For a child,
take relatively shallow breaths, about 20 per minute. Continue until
victim breathes for himself.
What Did You Learn? True or False
1. A broken arm should be splinted before artificial respiration is
applied to a victim who is not breathing.
2. A person who has been severely shocked with an electric current
should lie down.
3. A doctor should be called even though you successfully have revived a
victim's breathing.
4. A fraction of an ampere through the human heart muscles can be fatal.
5. A copper wire would provide a better path than your body for stray
currents, therefore all appliances should be grounded if possible.
6. Outside wires are never a hazard because they are covered with
insulation when they are installed.
7. Cords need not be repaired until you can see bare wires.
8. Tuning in an AC radio while you are bathing is always dangerous, even
though your hands are dry.
9. In an emergency, a broom is an acceptable tool for prying a victim
off a high tension wire.
10. In mouth-to-mouth breathing, an adult's lungs should be filled 12
times per minute and a child's 20.
Demonstrations You Can Give
Show how to deal with an electrical first aid "problem" given to you by
your leader.
For More Information
Ask your leader to have a first aid expert put on a demonstration. (Many
industrial plants and power suppliers have such people.)
LESSON NO. B-12
Credit Points 3
HOW ELECTRICITY HEATS
In ancient times, people thought that heat was a material just as air
is. They called it "caloric". When something got warm, they said,
caloric flowed into it. When something cooled off, caloric flowed out of
it. It did not bother them that they could not see caloric. They could
not see air either!
Now we know that heat is not a material. It does not take up space. It
does not weigh anything. Instead, it is a form of energy. And when we
say that heat is a form of energy, we mean that it can be used to do
work.
What to Do
1. Make a simple resistance heater.
2. Make some popcorn by:
(a) conduction (b) convection (c) radiation
"Resistance" Makes Heat
There are at least four ways that electricity can make heat. The one
that we'll cover here is _resistance_ heating. (The others are:
_dielectric_ heating, where the lines of force of an electrostatic field
pass through a non-conductive material and heat it; the _heat pump_,
which is a refrigerator in reverse; and _electronic_ heating, which uses
high frequency waves similar to radio waves to create high speed
movement of the molecules or tiny particles which rub together to make
heat.)
_Resistance_ heating occurs because every conductor of electricity
opposes the flow of current through it. Some conductors resist more than
others. When they do, a certain amount of warming takes place. The more
resistance that is offered, the more heating there is.
Some materials, like silver, copper, and aluminum, offer little
resistance. We say they are good conductors.
Other materials, like iron, offer more resistance. They are still
conductors, but not as good as the others mentioned.
The _size_ of the conductor, and its _length_ are the other two things
that affect its resistance. The _smaller_ it is, the greater its
resistance. Also, the _longer_ it is, the greater its resistance.
Therefore, when we only want to _move_ electricity from place to place,
we want relatively large, "good" conductors. Here, we do not want to
make heat. In fact, we want to avoid it, because too much heat in the
wrong place can cause a fire.
But when we want heat, we choose relatively small, "poor" conductors,
and the more heat we want, the longer they must be. If you will think of
the filament inside a lamp bulb; you may recall that it is a very fine
wire, coiled so as to get a maximum length, and made of tungsten which
has a high resistance.
Because of all these factors, this filament glows at a white heat, and
is a source of both light and heat.
Make a Simple Resistance Heater
_Materials you will need_:
1 dry cell battery
1 foot iron picture wire
Pliers
Use a short strand of iron picture wire and hook the ends to the
terminals of a dry cell battery. Use pliers so that you do not burn your
fingers. Disconnect the wires as soon as they become hot. Tell why the
wires heat.
Conduction is "Touching" Heat
Conduction occurs when you set a pan containing food right on a heating
element. An egg cooking in a hot frying pan is a good example of
conduction at work. This method is the most efficient single way of
using electric heat for cooking.
Convection Depends on Air
Convection warms food in pans that are not actually touching the heating
element. It uses the hot air around the element to carry heat to the
pan.
Your oven in your range works by convection. Most houses are warmed in
winter in the same way. The heat produced in a furnace warms the air as
it circulates through. This air in turn keeps your body warm.
Radiation is Like the Sun
Radiation heating is more difficult to explain. It results when heat or
energy waves strike an object and are converted into heat. The energy we
receive from the sun is a good example. When you are wearing dark
clothes on a chilly day, you may become uncomfortably hot. The sunshine
warms you even though the air around you has not been heated. Radiant
energy has a way of being absorbed by dark objects and reflected by
light colored or shiny surfaces. Did you ever notice how snow melts
faster on a black top road than it does on a concrete road?
The electric heat lamp is one of the most familiar sources of radiant
heat. Other examples are panels and cables that are built into the walls
and ceilings of homes to provide heat.
Make Popcorn 3 Ways
How do you make popcorn? Did you know that you can do this kind of a
heating job three different ways?
_Materials Needed_
Popcorn
Cooking oil or shortening
Salt and butter
4-qt. saucepan, with cover. (A glass cover
is preferred.)
Potholder
Electric range
2 250-watt heatlamps
2 spring clamp type lampholders
Wire mesh corn popping basket or wire
mesh kitchen strainer (improvise a
screen wire cover)
_First_, make popcorn the way you usually do. Set a front surface unit
control on the range at "medium high". Pour enough oil to very lightly
cover the bottom of the pan. When the pan is hot, pour in enough popcorn
to cover the bottom with one layer of kernels. Use the potholder in one
hand to hold the cover on, and with the other move the pan back and
forth across the unit. When the popping stops, remove from the heat.
How did the heat get to the popcorn?
_Second_, make popcorn in the oven. Add the oil to the pan, cover it and
put it in the oven. Turn the oven on, with the automatic control set at
400 deg. When the oven indicator light goes off, this means that the proper
temperature has been reached. With the potholder, remove the pan and add
one layer of popcorn kernels. Replace the pan in the oven. When the
popping stops (listen for it) remove the pan.
What kind of heating took place here?
_Third_, make popcorn with the heat lamps. Clamp the lampholders to the
back of a chair or other vertical support. They should be 6 to 8 inches
apart and pointed directly at each other. Put about 2 tablespoonfuls of
popcorn in the Wire basket or strainer. Do not add oil. Hold the basket
midway between the two lamps. When the popping stops, turn off the
lamps.
What kind of heating was this?
Now, butter and salt the popcorn you have made and share it with others.
What Did You Learn?
1. How is heat transferred from one body to another?
2. Could chicks or pigs receive warmth from a heat lamp without the air
in the pens becoming warm? Explain.
3. How does a broiler unit in a range cook meat?
4. How does an oven bake food?
5. Tell why iron picture wire was used instead of copper wire for your
heating demonstration.
LESSON NO. B-13
Credit Points 2
MYSTERIOUS MAGNETISM
In ancient times, people found certain rocks that clung together in
bunches. These rocks were very mysterious. People didn't understand them
and many superstitions grew up about lodestones, as these rocks were
called. Lodestone (sometimes spelled loadstone) means leading stone.
People even told Columbus not to sail out of sight of land because a
giant lodestone was just over the horizon waiting to pull all the nails
out of his ships.
The Chinese were the first to use magnets. They found that if you hung a
lodestone by a string, one end of the stone would always point in the
direction of the North Star. They had the first magnetic compasses.
An artificial magnet can be made by stroking or gently rubbing a piece
of steel with a lodestone. This piece of steel then can be used to
magnetize another piece of steel. This can be continued on and on.
Lodestones are not always available but you can get the same results
with an electric current. So, magnetism and electricity are very closely
related.
What to Do
Learn about magnetism by doing the experiments that follow.
Seeing is believing!
Materials You Will Need
2 dry cell batteries (#905)
A few feet of No. 18 bell wire
3 steel knitting needles or similar hard steel
2 ft. of light thread
Sheet of light cardboard or stiff paper
Permanent magnet (bar or horseshoe)
Compass
1 or more large nails or spikes
Red and black china-marking pencils or crayons
Iron filings
Wire cutters
Carpet tacks
(Iron filings usually can be found under the grinding wheel in a shop.
If you can't find any, rub some steel wool pads together to produce bits
of metal that will do.)
"See" a Magnetic Field
Cover the permanent magnet with the cardboard or paper. Sprinkle iron
filings on the paper. Tap the paper and note the pattern formed. Strings
or lines of filings pass from one pole of the magnet to the other. The
area covered by the filings is the center of the magnetic field. To
remember this, you might compare the magnetic lines of force that
arrange the iron filings to the contour strips in a farmer's field.
This magnetic field is one of the important things in our everyday life
with electricity. If it were not for the magnetic field, we would not
have electric motors. Telephones, radios, television, and many other
things we use every day also depend on this magnetic field.
[Illustration: Figure 1]
Make an Electro-Magnet
You can make magnetism work for you by winding several turns of
insulated wire around one or more large nails or spikes (soft iron).
Connect one end of the wire to the battery. Touch the other end of the
wire to the other terminal for a few seconds and see how many tacks you
can pick up. Repeat the experiment using as many turns as possible. How
many more tacks were you able to pick up?
[Illustration: Figure 2]
You have made what we call an electromagnet. When you disconnect the
wire, the nails fall off. This is one of the advantages of an
electromagnet. We can turn magnetism on and off as we wish. Picture a
crane operator throwing the switch and picking up scrap iron and steel.
Then he opens the switch to drop the scrap metals.
Soft iron can be magnetized easily as you have just seen, but loses its
magnetism in a short time. Steel is harder to magnetize but holds its
magnetism almost indefinitely.
Make a Permanent Magnet
Wrap the insulated bell wire around the steel knitting needle. The wire
should be wrapped the full length of the needle. One end of the wire is
connected to the battery. The other end of the wire is then touched for
just a few seconds to the other terminal. This should make the needle
into a permanent bar magnet. If you did not get results, try two
batteries in series, wind more turns of wire on the needle, and leave it
connected a little longer. Do the same thing with the second knitting
needle. In the same way, you can magnetize a screwdriver, so that you
can use it to pick up and hold steel screws. Don't do it unless you want
your screwdriver to be magnetized.
[Illustration: Figure 3]
See How They Attract and Repel
Take one of the magnetized needles and hang it with a thread. A thread
stirrup (Figure 4) will help keep it level. Be sure it is not near other
large pieces of steel. Watch the needle. Does it settle down, pointing
in one direction? (Check to see if this is the same direction as your
compass). If it does, you have made a compass. The tip of the needle
pointing north is called the North Pole (North-seeking pole). The other
end is called the South Pole. Mark the North Pole with a stroke of the
red marking pencil. Mark the South Pole black. Do the same thing with
the second needle. You can show this with a sewing needle, and a notched
cork, and a bowl of water. Rest the needle in the notched cork, and
float it on the water.
[Illustration: Figure 4]