The electron beam in the CRT excites the phosphor on the face of the CRT so that it glows. The 'glow' is simply releasing the energy that it previously absorbed from the electron beam. The glow dimishes with time as the energy is released. Persistence refers to the amount of time the glow is perceptable to the human eye after the beam is no longer providing energy to the phosphor.

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A higher anode voltage increases the electron velocity (higher energy electrons). If the electron velocity increases too much, x-rays may result.

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A charge-coupled device (CCD) samples an analog signal and passes it in stages from the input to the output.

A CCD is a chain of capacitors separated by MOSFET transistors. Both the capacitors and the MOSFETs are made in metal-oxide semiconductor material itself. The MOSFETs are used to transfer the voltage from one capacitor to another in the chain until it reaches the output, where it can be converted to digital.

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Light sensitive materials are used to induce a voltage on the capacitors in a CCD. The image is captured in a two dimensional array where the charge on each capacitor is proportional to the light at that point. The image in the array is then shifted to the outputs one line at a time, where it can be further processed for immediate display or stored for later use.

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The liquid crytal material responds to an applied voltage, which changes its light refraction. This allows the material to go from nearly transparent to almost opaque, making it appear black.

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Permeability is a measure of the response of a given material to a magnetic field. The measure is relative to the magnetic field strength observed with no core. A higher permeability will result in a higher inductance for a constant number of turns on the toroid. It is measured in henries per meter. Air has a permeability of 1. So, the permeability of the material used in the core of the toroid will have the biggest impact on its inductance

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This is simply memorizing that toroidal cores support a frequency range up to 300 MHz.

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Powdered-iron cores have better temperature stability but the permeability is lower. Ferrite cores have higher permeability but the temperature stability is not as good. If temperature stability is more important than size, then powdered-iron core may be desirable.

Hint: The "I" in Iron means "I" like the symbol for current measured in amps.

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The ferrite bead (small sphere of ferrite with a hole through it) is a very small core and acts as a filter to suppress higher frequency noise.

https://en.wikipedia.org/wiki/Ferrite_bead

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Because of the circular geometry of the toroidal core, it contains most of the magnetic field inside the core. This makes toroids well suited for use on circuit boards where magnetic field interference with other components is undesirable.

Hint: All answers start with "Toroidal cores". What is important is that the the correct answers' 3rd word comes first alphabetically among all the answers. The "C" in confines is the first alphabetically.

Another hint: the question has the word "core" twice and so does the answer.

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The equation for a ferrite toroid is:

\[N = 1000 \times \sqrt {\frac{L}{A_L}}\]

Where:

\(N\) is the number of turns;
\(L\) is the inductance in millihenries;
\(A_L\) is the inductive index (which must be given in millihenries per 1000 turns for this equation).

So,

\begin{align} N &= 1000 \times \sqrt {\frac{L}{A_L}}\\ &= 1000 \times \sqrt {\frac{1}{523}}\\ &= 43.7\\ &\approx 43\text{ turns} \end{align}

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The approximation formula for a powdered-iron toroid is: \[N = 100 \times \sqrt{\frac{L}{A_L}}\]

Where:
\(N\) is the number of turns
\(L\) is the inductance in microhenries
\(A_L\) is the inductance index
     (and must be in microhenries per 100 turns to
      be consistent with the units for \(L\)).

So, \begin{align} N &= 100 \times \sqrt{\frac{L}{A_L}}\\ &= 100 \times \sqrt{\frac{5}{40}}\\ &= 100 \times \sqrt{0.125}\\ &= 35.4\\ &\approx 35\text{ turns} \end{align}

The multiplier for henries in the formula doesn't matter as long as both \(L\) and \(A_L\) use the same multiplier. For example, \(L\) can be henries if \(A_L\) is henries per 100 turns; \(L\) can be millihenries as long as \(A_L\) is millihenries per 100 turns

The only answer with a five (5) so, 5 microhenries = 35 turns. Albert WP4AES

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Because electromagnetic deflection is not accurate enough for higher frequencies, electrostatic deflection must be used. This is common in oscilloscopes and other high frequency devices where higher precision is desireable.

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Refer to question D06 for a discussion of what a CCD is. Because it simply stores voltages on capacitors, the CCD cannot act as an A/D converter.

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LCD's are definitly low power alternatives, which is why they are popular in hand-held calculators and other devices that rely on small batteries.

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Because ferrite toroids have a higher permeability than powdered-iron toroids, the inductance for a given number of turns is increased. Therefore, smaller inductors and inductors with fewer turns are possible using ferrite toroids.

Memory tip:
Ferrite Toroids = Fewer Turns

Hint: 'Inductor' is in the question and 'Inductance' only appears in the correct answer.

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