Download AC frequency and wavelength

Things left Out of Other Books on Basic Electronics,
Electronics for the Gaming Industry
DC - Direct Current
DC is electrical current that does not change in polarity or direction. The more
positive lead is always the more positive. Curent only flow in one direction through the
circuit. Voltage may change in value, current may change in value, but neither may
change in polarity. Also speed does not change in AC or DC. Other books on basic
electricity describe electrons as sleeping. When a voltage is applied they speed up to a
maximum then slow down again and stop. I agree with the need to simplify the facts
when covering bascs, but our descriptions should not be misleading. The electrons are
always in motion, around the atom if nothing else. When we apply a voltage our pressure
is small at first and few current carriers (electrons or holes) flow. Our current is small, but
the speed is the same.
Electrical force (Voltage, E or V) only pushes in one direction. Negative voltage
always pushes the electrons in the same direction, negative to positive. If we have a path
current will flow (Amps, I or A). How much current we will have flowing depends on the
resistance of our path (R or ).
Ohm's law shows the relationship between Volts, Amps and Ohms.If we know
two values, we can always fiind the third value.
E = I x R (Voltage equals Current times Resistance)
I = E/R (Current equals Voltage divided by Resistance)
R = E/I (Resistance equals Voltage divided by Current)
The other popular value we hear alot is Watts. The power consumed (or
dissipated) in a circuit. Watts (W or P in formulas) is simply a mathematical calculation
of Volts multiplied by Current.
Of course there is a few hundred hours nmore to be said on these subjects, but that
goes deeper than is necessary for the position of Slot Technician. We won't get into the
more complicated stuff until we get to Bench Technician material.
Frequency, Time Period, and Wavelength
Frequency of an AC signal is a simple matter of how many cycles the signal goes
through in a second. (Cycles Per Second, or Hertz). An AC signal will start from zero
volts, increase to some maximum positive voltage, decrease back to zero, increase to
some maximum negative voltage, and return to zero. This is one cycle.
If the signal is 60 Hz, it is making 60 cycles per second. Each cycle, obviously,
takes 1/60th of a second, or 0.0166666 Seconds. This is the Time Period of a 60 Hz
signal. The time it takes for the signal to make one complete cycle.
If this electricity is traveling at the speed of light (186,000 miles per second, or
300,000 km per second) the distance it would travel in one Time Period is the
Wavelength. This is true whether we are talking about current flow through a wire, or a
magnetic field moving through space. At 186,000 miles per hour for 0.016666 seconds,
we have a Wavelength of about 3100 miles.
It would make sense that the higher the frequency, the shorter the time period, and
the shorter the wavelength. As the frequency of our cell phones has increased, the
antenna has gotten shorter. At 2.4 GHz systems, the antenna is a stub built inside the case
of the phone, and is hardly noticeable at all.
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Things left Out of Other Books on Basic Electronics,
Electronics for the Gaming Industry
AC characteristics
If we again consider our AC signal going from zero, to some peak positive level,
back to zero, to some peak negative level, returning to zero, we should consider how
much power we actually have available. If we take an incandescent lamp, working at 120
V DC, how much voltage, AC, do we have to apply to get the lamp to light to the same
brightness as 120 V DC?
If we were to draw a graph of our power available from AC, we would see a
signal starting from zero, increasing to some peak maximum, decreasing to zero,
increasing to the peak again, and returning to zero. (Polarity doesn’t matter.) Most of the
time our signal is far below the peak value. How much effective power do we have?
As long as we are talking about a sine-wave signal, like our line power, we find
that the effective power is Peak x 0.707, (or Peak / 1.414). The Peak value then can be
calculated as Effective x 1.414, (or Effective / 0.707).
It therefore takes 170 Volts (Peak) to get the light to light on AC to the same
brightness as 120 VDC. This Effective value is sometimes called the RMS (Root Means
Square), or effective, value.
Don’t confuse this with the Average. Average is 0.636 of the Peak value.
Keeping in mind that our signal goes both positive to this Peak value, then
negative to this Peak value, our signal actually goes +170, then –170, for a total of 340
Volts (Peak to Peak), to get the same effective power we would from 120 V DC. We rate
the line voltage in the effective (RMS) value.
We can rate Voltage, Current, Power, or anything else that follows a sine wave,
by these Peak-to-Peak, Peak, RMS, or Average, values. As long as we are talking about a
sine wave, the formulas are the same. (Not all signals we will see are sine waves.)
Peak x 2 = Peak-to-Peak
Peak-to-Peak / 2 = Peak
Peak x 0.707 = RMS
or
Peak x 0.636 = Average
RMS x 1.414 = Peak
Peak / 1.414 = RMS
or Peak / 1.57 = Average
or RMS / 0.707 = Peak
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Things left Out of Other Books on Basic Electronics,
Electronics for the Gaming Industry
Frequency spectrum of electromagnetic radiation
The range of available frequencies for electromagnetic radiation is, in deed, quite
broad.
Below 500,000 Hz, we have “Long Wave” radio, used for maritime radio.
Around 1,000,000 Hz (1 MHz, or 1 Mega-Hertz), we have AM radio.
Between 2 MHz and 88 MHz we have “Short Wave” radio.
Around 100 MHz we have FM radio.
Between 100 MHz and 300 MHz, we have television.
Between 300 MHz and 600 MHz, we call it “Micro Wave”.
Most of today’s cell phones and satellite communications come in to play from
600 MHz to 3,000 MHz (or 3 GHz, Giga-Hertz).
Above 3 GHz few people venture except the military. Even military systems top
out around 150 GHz, but that is not the end of the story. Above the hundreds of GHz
range is the area we perceive as heat.
Above heat, we get into Infrared. This is still only electromagnetic radiation.
Above Infrared there is a very narrow spectrum of electromagnetic radiation that
the rods and cones inside our eyes perceive as visible light. At the low end we see red,
then orange, yellow, green, blue, and violet.
Above violet is a wide region of Ultraviolet.
Above this range we have little more than solar noise. This is a broad range made
up of radiation attributed to subatomic particles. The wavelengths correspond to
dimensions smaller than atoms. Above this we reach the limits of our knowledge, and in
our ignorance we call electromagnetic radiation beyond this “Cosmic Radiation”.
For the curious, the question comes up, “is there a maximum frequency?” If an electron must
travel from atom to atom to create an electromagnetic field, then the maximum frequency would be the
wavelength equal to the distance between two atoms. Since our atoms vary in size from about 0.50
Angstroms to just over 2.0 Angstroms. Given this, our maximum frequency would be somewhere around 1.0
to 5.0 with 18 zeros after it. If we try to consider a higher frequency, can we get so high a frequency that
the electron is not making a complete orbit around the atom? Can we extend this to the idea that we can get
an electron to oscillate so fast it is actually not moving at all?
For you Trekies, I often get the question about “Sub-Space Transmitters”. Where is the frequency
of Sub-Space Transmitters? In the imagination of the authors, only. Many aspects of “science” we find in
movies and television exists only to support the plot of the program. Such concepts are more Science
Fantasy, than Science Fiction. Knowledge of these truths only makes the movies a little less entertaining.
Sorry, Captain Kirk. Scotty will never be able to “Beam you up”.
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Things left Out of Other Books on Basic Electronics,
Electronics for the Gaming Industry
1.
What is the formula for Ohm’s Law to find Current?
2.
What is the formula for Ohm’s Law to find Voltage?
3.
What is the formula for Ohm’s Law to find Resistance?
4.
What do we multiply together to find Watts?
5.
What is the Peak value for an RMS voltage of 120 V?
6.
What is the RMS value for a Peak current of 1 Amp?
7.
What is the effective power of your Stereo that is rated at 100 Watts, Peak-toPeak?
8.
What do radio waves, microwaves, heat, light, and cosmic waves have in
common?
9.
What is the approximate wavelength of an AM radio station?
10.
What is the approximate wavelength of an FM radio station?
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Things left Out of Other Books on Basic Electronics,
Electronics for the Gaming Industry
1. What is the formula for Ohm’s Law to find Current? I = E/R
2. What is the formula for Ohm’s Law to find Voltage? E = I x R
3. What is the formula for Ohm’s Law to find Resistance? R = E/I
4. What do we multiply together to find Watts? Volts and Amps
5. What is the Peak value for an RMS voltage of 120 V? About 170 V
6. What is the RMS value for a Peak current of 1 Amp? About 0.707 Amps
7. What is the effective power of your Stereo that is rated at 100 Watts, Peak-toPeak? 100 / 2 = 50 Watts, Peak. 50 x .707 = about 35 Watts.
8. What do radio waves, microwaves, heat, light, and cosmic waves have in
common? They are all electromagnetic radiation.
9. What is the approximate wavelength of an AM radio station? 1 MHz = 982 ft.
10. What is the approximate wavelength of an FM radio station? 100 MHz = 9.82 ft,
3.27 yards or about 117 inches
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