The AC current density is strongest at the surface of a conductor, and the magnitude decreases exponentially as you get farther away from the surface. Several variables affect this distribution, with frequency being one of them. You just have to remember that the current density at the surface increases with increasing frequency, leading to a 'thinner' RF current.

The skin effect governs how far RF signals penetrate a given material.

Memory Aid: The question refers to conductor skin effect. The portion of the correct answer - “…current flows close to the surface,” refers to “skin” (on the surface).

Silly Hint: Where can you find a lot of skin on people? In their creases ("Increases" is in the right answer).

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Any wire has self inductance, which increases with the length of the wire (among other things). Since the impedance of an inductor is proportional to frequency, it is usually safe to ignore the self inductance of short wires at low frequencies. But for VHF and above a wire's self inductance may have significant inductive reactance. This reactance is often unwanted and can be minimized by keeping connections short.

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Voltage and current are always out of phase by 90 degrees through a reactive load (i.e. a capacitor or an inductor). Voltage and current are always in phase in a resistive load.

The reason for this is reactive loads store and release energy. If you apply voltage to a capacitor, it charges and as it does so current starts to flow into it after a delay. If you send a current through an inductor an electric field starts to form and voltage increases after a delay.

For capacitors current leads voltage, for inductors voltage leads current. The mnemonic "ELI the ICE man" helps remember this:

• ELI: E (voltage) comes before I (current) for L (inductance)
• ICE: I (current) comes before E (voltage) for C (capacitance)

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The answer is somewhat bogus as with microstrip and other high frequency designs, you use controlled lengths of connections (transmission lines) to purposely introduce phase shift which is part of tuning and matching.

In other words, short connections are not necessary other than to cut down on loss and parasitic radiation.

But if you wanted to minimize phase shift (which is rarely a design goal), then you would want short connections.

Just remember it is the only answer with "phase shift" in it.

Hint: It's also the only answer with the word "connection" in it, which is also in the question.

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All capacitors have parasitic inductance, also known as equivalent series inductance (ESL). ESL is the result of the size of the capacitor's package. Smaller capacitors tend to have lower ESL than larger capacitors. For example, large electrolytic or tantalum capacitors have higher ESL than small ceramic capacitors.

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Self-resonance happens when you have both inductance and capacitance in series.

Real world components have parasitics-- every component contains resistance, inductance, and capacitance in addition to the values it is designed to have.

In an inductor, adjacent wire acts similarly to the plates of a capacitor to create a small amount of parasitic capacitance between each turn. This combination of inductance and capacitance causes resonance.

Caution: Distractor Coupling is a general term for a transfer of energy, which may involve inductor fields. It typically refers to connecting two physically separate circuits.

Inter-turn capacitance describes a specific field effect occurring in the inductor, thus it's the most correct answer.

HINT: Both "self-resonance" in the question, and "inter-turn" in the answer, are hyphenated words.

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Caution:
While it's true that distractor The component’s inductance and capacitance are involved in self-resonance, this choice is too general.
The correct answer The component’s nominal and parasitic reactance also involves inductance and capacitance, and identifies which is parasitic. This choice is more specific, and thus more correct.

We know that a LC circuit is a resonant circuit. I like to think of this question as "If it is a capacitor, the parasitic inductance will form an LC circuit. If it is an inductor, then the inter-turn capacitance will cause the C part of LC"

In essence, this question is asking, "how is it possible for these components to self resonate?" A resonant antenna can be represented by "LCR", which means that the wire's resistance, inductance, and capacitance are all combined. In a perfectly resonant antenna, the L and C reactive elements cancel out and you are left with just the wire's resistance. In a LC resonant circuit, the same thing happens, but with inductors and capacitors.

All a capacitor is is two conductors separated by an insulator. That mean that an inductor's turns have a small natural capacitance, which can form a resonant circuit with itself. However, a capacitor can also have a small amount of inductance, which combines with it's actual capacitance value to form another resonant circuit. So, the components nominal value and parasitic value can combine to form an LC resonant circuit.

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Skin effect is a phenomenon where alternating current (AC) tends to flow mainly on the surface of a conductor rather than through its entire cross-section. At radio frequencies (RF), this effect becomes more pronounced, causing the current to be confined to a thin layer on the conductor's surface.

This increases the resistance and results in greater power loss. In film capacitors used at RF, the skin effect causes higher losses because the current is restricted to the thin surface of the conductive films, leading to increased resistance and energy dissipation.

Hint: Skin and film are often synonymous.

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The question states both ideal inductors and capacitors, so think perfect. The current just passes from the inductors (magnetic field) to the capacitors (electric field), back and forth so none of the power is lost or dissipated.

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From the ARRL Antenna book:

the electrical length of a linear circuit such as an antenna wire is not necessarily the same as its physical length in wavelengths or fractions of a wavelength. Rather, the electrical length is measured by the time taken for the completion of a specified phenomenon.

As the diameter increases the resistance decreases, which in effect lengthens the effective "electrical length" of the wire. Thus you could have two wires of differing physical length which are both electrically e.g. "\(1\over2\) wavelength" at the same frequency because the shorter one has a larger diameter.

So, to restate again: the electrical length increases as the diameter increases.

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Only resistance (real component of impedance) consumes power. The values for the resistor, 100 ohms, and current, 1 A, are given.

\begin{align} P_{\text{real}} &= I^2 R\\ &= (1 \text{ A})^2(100 \:\Omega)\\ &= 100 {\text{ W}} \end{align}

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Capacitors resist change in voltage and inductors resist change in current each by storing energy and releasing it as voltage and current fluctuate. This is called reactance. Unlike resistance, no actual power is dissipated by reactance. In purely reactive circuits there will still be measurable voltage and current. The product of this voltage and current is called "wattless" power, measured in volt-ampere reactive (VAR).

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