More Than You Wanted to Know about Electricity
More Than You Wanted to Know about Electricity and Electronics Yes, there will be math
Metric System Factors Prefix Factor Giga 1, 000, 000 x 10^9 Billion! Mega 1, 000 x 10^6 Million Kilo 1, 000 x 10^3 Thousand Unit 1 x 10^0 base Centi 0. 01 x 10^-2 Hundredth Milli 0. 001 x 10^-3 Thousandth Micro 0. 000001 x 10^-6 Millionth Nano 0. 00001 x 10^-9 Billionth Pico 0. 0000001 x 10^-12 Trillionth!
Ohm's Law E = I • R E == Voltage (in Volts) I == Current (in Amps) R == Resistance (in Ohms) E I R
Examples Voltage = 110 V Resistance = 10Ω Amperage = ? ? Amperage = 15 A Resistance = 10Ω Voltage = ? ? Voltage = 12 V Amperage = 2. 5 A Resistance = ? ?
Examples Voltage = 110 V Resistance = 10Ω Amperage = 11 A Amperage = 15 A Resistance = 10Ω Voltage = ? ? Voltage = 12 V Amperage = 2. 5 A Resistance = ? ?
Examples Voltage = 110 V Resistance = 10Ω Amperage = 11 A Amperage = 15 A Resistance = 10Ω Voltage = 150 V Voltage = 12 V Amperage = 2. 5 A Resistance = ? ?
Examples Voltage = 110 V Resistance = 10Ω Amperage = 11 A Amperage = 15 A Resistance = 10Ω Voltage = 150 V Voltage = 12 V Amperage = 2. 5 A Resistance = 4. 8Ω
Power is the ability to do work A measure of energy (or mass moved) over time P=I∙E P I E
Examples Voltage = 110 V Amperage = 15 A Power = ? ? Power = 1500 W Amperage = 20 A Voltage = ? ? Power = 100 W Voltage = 12 V Amperage = ? ?
Examples Voltage = 110 V Amperage = 15 A Power = 1650 W Power = 1500 W Amperage = 20 A Voltage = ? ? Power = 100 W Voltage = 12 V Amperage = ? ?
Examples Voltage = 110 V Amperage = 15 A Power = 1650 W Power = 1500 W Amperage = 20 A Voltage = 75 V Power = 100 W Voltage = 12 V Amperage = ? ?
Examples Voltage = 110 V Amperage = 15 A Power = 1650 W Power = 1500 W Amperage = 20 A Voltage = 75 V Power = 100 W Voltage = 12 V Amperage = 8⅓A
Direct Current vs. Alternating Current DC – current flows in one direction, negative to positive, voltage is constant AC – current flows in both directions, voltage varying from max in one direction to max in the other direction Electronics typically powered by ? ? Radio transmission is ? ? Modulated audio is ? ?
Direct Current vs. Alternating Current DC – current flows in one direction, negative to positive, voltage is constant AC – current flows in both directions, voltage varying from max in one direction to max in the other direction Electronics typically powered by DC Radio transmission is ? ? Modulated audio is ? ?
Direct Current vs. Alternating Current DC – current flows in one direction, negative to positive, voltage is constant AC – current flows in both directions, voltage varying from max in one direction to max in the other direction Electronics typically powered by DC Radio transmission is AC Modulated audio is ? ?
Direct Current vs. Alternating Current DC – current flows in one direction, negative to positive, voltage is constant AC – current flows in both directions, voltage varying from max in one direction to max in the other direction Electronics typically powered by DC Radio transmission is AC Modulated audio is AC!
RMS = Root Mean Square Voltage in an AC system is typically measured in RMS
Calculating Frequency or Wavelength (m) / Time (s) = Speed of Light (300, 000 m/s) Remember, Frequency is measured in Hz, or “per second” (1/s) Wavelength (m) x Frequency (Hz) = Speed of Light (300, 000 m/s) Algebra Time! Wavelength = Speed of Light / Frequency c or Frequency = Speed of Light / Wavelength λ f c “lambda” == wavelength (in meters) frequency (in Hz) speed of light (in m/s) λ f
Examples Frequency = 146. 000 MHz Wavelength = ? ?
Examples Frequency = 146. 000 MHz Wavelength = c (300, 000 m/s) / 144, 000 Hz =
Examples Frequency = 146. 000 MHz Wavelength = c (300, 000 m/s) / 144, 000 Hz = 2. 08333… m about 2 meters! Wavelength = 80 m Frequency = c (300, 000 m/s) / 80 m =
Examples Frequency = 146. 000 MHz Wavelength = c (300, 000 m/s) / 144, 000 Hz = 2. 08333… m about 2 meters! Wavelength = 80 m Frequency = c (300, 000 m/s) / 80 m = 3, 750, 000 Hz 3. 750 MHz or 3, 750 k. Hz
Inductors and Capacitors Impedance is the opposition to the flow of current in an AC circuit (measured in Ohms). Reactance is the opposition to the flow of current caused by capacitance or inductance. What causes opposition to the flow of alternating current (impedance) in an inductor? Reactance! What causes opposition to the flow of alternating current in a capacitor? Reactance!
Inductors and Capacitors How does an inductor react to AC? Reactance increases as frequency increases.
Inductors and Capacitors How does a capacitor react to AC? Reactance decreases as frequency increases.
Impedance What happens when the impedance of a load is equal to the impedance of the power source? The source can deliver the maximum amount of power to the load. This is why we do impedance matching when hooking antennas to transmitters!
Impedance Why would you use an impedance matching transformer? To maximize the transmitted power! What can you use to match the impedance at radio frequencies? A transformer A Pi-network (or LC network) A length of transmission line All of the above!
Pi network?
Decibel Scale (d. B) Measuring increases or decreases in power or noise. Logarithmic Scale
Decibel Scale minus (-) d. B plus (+) one half 3 2 times one quarter 6 4 times one tenth 10 10 times What d. B change represents a factor of two increase or decrease in power? Approximately 3 d. B
Questions? We are about half-way through section G 5 of the
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