This one can throw people off a bit; many confuse Inductance and Capacitance, which are pretty similar on this question.
A capacitor is a passive component that consists of at least one pair of conductors separated by a dielectric (an insulator). When voltage is applied to the capacitor (creating a difference in potential between the two) it creates an electric field across the dielectric which stores energy. The easiest way for me to remember these is that an inductor, being a coil of wire, is used to create an electromagnet (you can make an electromagnet by wrapping a coil of insulated wire around a nail, for example), and so an inductor stores energy in a magnetic field. The capacitor stores energy in an electric field.
Once again:
What is the ability to store energy in a MAGNETIC field called? Inductance
What is the ability to store energy in an ELECTRIC field called? Capacitance
MICE acronym for above = Magnetic & Inductance pair while Capacitance & Electric pair
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Tags: electronics definitions capacitance arrl chapter 3 arrl module 5
The basic unit of capacitance, the Farad, is named for the physicist Michael Faraday.
The other units listed here are:
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An inductor is a coil of wire, usually around a non-ferrite (nonmagnetic) core. The basic unit of inductance is the henry. Whenever you make a coil of wire, it creates a magnetic field; think of an electromagnet, which is basically an inductor with a ferrite core. The ability to store energy in such a field is Inductance. So remember -- inductance creates a magnetic field.
Capacitance has a very similar (and in fact opposite) effect to an inductor and creates an electric field.
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Tags: electronics definitions inductance arrl chapter 3 arrl module 5
An inductor is a passive electrical component that stores energy in a magnetic field; its unit is the henry, which is named for Joseph Henry.
The other (incorrect) answers here are:
Study Tip: Consider using the line "Henry was inducted into the hall of fame" to jog your memory.
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Tags: electronics definitions inductance arrl chapter 3 arrl module 5
Hertz is the standard unit for frequency, as used in the SI unit system. It is defined as the number of cycles per second of something periodic. For example a quartz clock ticks at \(1\)Hz. The wall outlet AC is set to \(60\)Hz. The tone of A just below middle C is \(220\) Hz. The unit is named after Heinrich Hertz](wiki/Heinrich_Hertz). Here is a graphical example from Wikipedia.
The other (incorrect) answers here are:
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RF is "Radio Frequency" - it's not reflected force or any of these other choices. Just learn this one.
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Radio waves are a type of electromagnetic (EM) radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 GHz to as low as 3 kHz, though some definitions describe waves above 1 or 3 GHz as microwaves, or include waves of any lower frequency. (Wikipedia)
EM waves are made up of magnetic field and electric field oscillations in phase with each other, but their direction is perpendicular.
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\[P={E}\times{I}\]
\[E=\frac{P}{I}\]
\[I=\frac{P}{E}\]
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Tags: formulas math electrical power electrical current electromotive force (voltage) power law arrl chapter 3 arrl module 4
\(P = I \times E\) \(=\) \(10 \times 13.8\) \(=\) \(138\) watts
The formula for electrical power is \(P = I \times E\).
"Power (in watts) equals Current (in amperes) multiplied by Potential Energy (in volts)."
\(P\) (watts) = \(10\) (amps)\(\times 13.8\) (volts)
\(10 \times 13.8 = 138\)
\(138\) watts
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Tags: math dc power electrical power electromotive force (voltage) electrical current power law arrl chapter 3 arrl module 4
Power is the rate of of electrical energy generation or consumption.
\(P = V \times I\) (watts \(=\) volts \(\times\) amperes)
Where \(P\) is power (\(W\)), \(V\) is voltage (\(V\)), and \(I\) is current (\(A\)).
\(P = 12V \times 2.5A = 30W\)
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Tags: math dc power electrical power electromotive force (voltage) electrical current power law arrl chapter 3 arrl module 4
\(P = I \times E\)
\(I = \frac{P}{E}\) \(=\) \(\frac{120}{12}\) \(=\) \(10\) amperes
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Tags: math ohm's law electrical current electrical power arrl chapter 3 arrl module 4
The inverse of resistance is conductance (the measure is the Mho - can you see how this is related to Ohm?). So that's not the answer.
The measure of \(Q\) is something covered on the General and Extra exams - it's too deep for the Technician exam. So that's not the answer.
Power handling capability? Power is measured in Watts, so the power handling capability would be measured in Watts. Components are certainly rated in things like Watts and Volts and even Amps, but none of those things are called impedance. So that's not the answer.
And that leaves "It is a measure of the opposition to AC current flow in a circuit."
Impedance, incidentally, is measured in Ohms.
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Impedance
is actually very similar to resistance
in many ways -- which makes sense, since impede
and resist
are roughly synonymous. Thus it makes sense that they share the same unit -- Ohms.
The main difference between resistance
and impedance
is that impedance
changes with frequency. Inductors pass direct current (frequency of \(0\)) but have a higher impedance
the higher the frequency, since inductors tend to resist changes in current. Capacitors have infinite impedance
with DC and the higher the frequency the lower the impedance (capacitors resist changes in voltage).
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M is the SI abbreviation for mega, indicating millions or \[\times10^6\] Hz is the SI unit abbreviation for Hertz or cycles per second.
Therefore the proper abbreviation for megahertz is...
Hopefully you will find this easy to remember as you will be seeing it a lot.
Visually, you might also notice that MHz is made up of all straight lines.
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