-8-
Antenna: The radio antenna is the cylindrical
component with a coil of fine wire wrapped around it.
The dark colored rod is made mostly of powdered
iron. Ferrite cores (rods made from powdered iron
and other oxides) make efficient antennas for almost
all transistor radios.
Transformer: If you wrap two wires from different
circuits around different ends of an iron bar then a
current flowing through the wire from the first circuit
will magnetically create a current in the wire from the
second circuit! If the second coil has twice as many
turns (more magnetic linkage) as the first coil then
the second coil will have twice the voltage but half
the current as the first coil. A device like this is called
a
transformer.
The magnetic field created in an iron bar by an
electric current in the coil around it can be harnessed
if the bar is allowed to rotate - it is a motor. It could
be used to drive the wheels of a car, for example. The
reverse is also true, if a magnet within a coil is
rotating then an electric current is created in the coil
- a generator. These two statements may not seem
important to you at first but they are actually the
foundation of our present society. Nearly all of the
electricity used in our world is produced at enormous
generators driven by steam or water pressure. Wires
are used to efficiently transport this energy to homes
and businesses where it is used. Motors convert the
electricity back into mechanical form to drive
machinery and appliances.
Speaker: A speaker converts electrical energy into
sound. It does this by using the energy of an AC
electrical signal to create mechanical vibrations.
These vibrations create variations in air pressure,
called sound waves, which travel across the room.
You “hear” sound when your ears feel these air
pressure variations. You need high current and low
voltage to operate a speaker, so we will always use
the transformer with the speaker. (Remember that a
transformer converts high-voltage/low-current to low-
voltage/high-current).
The earphone is similar to the speaker, except that it
is more sensitive (and moveable). It is an efficient,
lightweight earphone that can be connected without
drawing too much electrical energy from the circuit.
For very weak sounds, the earphone is best; for
stronger sounds, you will use the speaker.
Batteries: The battery holders are designed to hold
six (6) “AA” batteries. Batteries supply the power for all
the experiments in your kit. When connecting wires to
the batteries, be sure you connect only to the terminals
noted. Terminals 119 and 120 provide 3 volts. Terminals
119 and 121 provide 4.5 volts. You need to be aware
that connecting too much voltage (you can get up to 9
volts from these battery connections) can damage
some parts (they can be burned out). So, be sure to
make the right battery connections.
Caution: When you connect wires to the batteries,
you must be sure to use the correct polarity: (+) and
(–) sides of the battery. With some parts and circuits,
components can be permanently damaged if you
reverse the polarity.
Summary of Contents for EP-130
Page 11: ... 11 I ENTERTAINMENT CIRCUITS ...
Page 26: ... 26 II BASIC SEMICONDUCTOR AND COMPONENTS CIRCUITS ...
Page 36: ... 36 III LED DIGITAL DISPLAY CIRCUITS ...
Page 41: ... 41 IV A TOUR THROUGH DIGITAL CIRCUITS ...
Page 49: ... 49 V MORE ADVENTURES WITH DIGITAL CIRCUITS ...
Page 64: ... 64 VI THE WORLD OF TRANSISTOR TRANSISTOR LOGIC ...
Page 77: ... 77 VII APPLICATION CIRCUITS BASED ON THE OSCILLATOR ...
Page 88: ... 88 VIII BASIC OPERATIONAL AMPLIFIER CIRCUITS ...
Page 116: ... 116 IX MORE ADVENTURES WITH OPERATIONAL AMPLIFIERS ...
Page 129: ... 129 X COMMUNICATION CIRCUITS ...