Power Education

The Q, quality factor, of a resonant circuit is a measure of the “goodness” or quality of a resonant circuit. A higher value for this figure of merit corresponds to a more narrow bandwith, which is desirable in many applications. More formally, Q is the ratio of power stored to power dissipated in the circuit reactance and resistance, respectively: Q = Pstored/Pdissipated = I2X/I2R Q = X/R where:

PARTS AND MATERIALS Paper tube, from a toilet-paper roll Bar of iron or steel, large enough to almost fill diameter of paper tube 28 gauge “magnet” wire Low-voltage AC power supply Incandescent lamp, rated for power supply voltage CROSS-REFERENCES Lessons In Electric Circuits, Volume 1, chapter 14: “Magnetism and Electromagnetism” Lessons In Electric Circuits, Volume 1, chapter 15: “Inductors” Lessons In Electric Circuits, Volume 2, chapter 3: “Reactance and Impedance—Inductive” LEARNING OBJECTIVES Effects of magnetic permeability

Impedance matching Because transformers can step voltage and current to different levels, and because power is transferred equivalently between primary and secondary windings, they can be used to “convert” the impedance of a load to a different level. That last phrase deserves some explanation, so let’s investigate what it means. The purpose of a load (usually) is to do something productive with the power it dissipates. In the case

Split-phase power systems achieve their high conductor efficiency and low safety risk by splitting up the total voltage into lesser parts and powering multiple loads at those lesser voltages while drawing currents at levels typical of a full-voltage system. This technique, by the way, works just as well for DC power systems as it does for single-phase AC systems. Such systems are usually referred to as three-wire systems rather than

So far, we’ve observed simulations of transformers where the primary and secondary windings were of identical inductance, giving approximately equal voltage and current levels in both circuits. Equality of voltage and current between the primary and secondary sides of a transformer, however, is not the norm for all transformers. If the inductances of the two windings are not equal, something interesting happens: transformer v1 1 0 ac 10 sin rbogus1 1 2 1e-12 rbogus2 5 0

PARTS AND MATERIALS One N-channel junction field-effect transistor, models 2N3819 or J309 recommended (Radio Shack catalog # 276-2035 is the model 2N3819) Two 6-volt batteries One 10 kΩ potentiometer, single-turn, linear taper (Radio Shack catalog # 271-1715) One 1 kΩ resistor One 10 kΩ resistor Three 1.5 kΩ resistors For this experiment you will need an N-channel JFET, not a P-channel! Beware that not all transistors share the same terminal designations, or pinouts, even if they

PARTS AND MATERIALS Low-voltage AC power supply (6 volt output) Two 1N4001 rectifying diodes (Radio Shack catalog # 276-1101) Small “hobby” motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) Audio detector with headphones 0.1 µF capacitor One toggle switch, SPST (“Single-Pole, Single-Throw”) It is essential for this experiment that the low-voltage AC power supply be equipped with a center tap. A transformer with a non-tapped secondary winding simply will not work for

Diodes can perform switching and digital logic operations. Forward and reverse bias switch a diode between the low and high impedance states, respectively. Thus, it serves as a switch. Logic Diodes can perform digital logic functions: AND, and OR. Diode logic was used in early digital computers. It only finds limited application today. Sometimes it is convenient to fashion a single logic gate from a few diodes. Diode AND gate

In the chapter on mixed-frequency signals, we explored the concept of harmonics in AC systems: frequencies that are integer multiples of the fundamental source frequency. With AC power systems where the source voltage waveform coming from an AC generator (alternator) is supposed to be a single-frequency sine wave, undistorted, there should be no harmonic content . . . ideally. This would be true were it not for nonlinear components. Nonlinear components draw current

This calculator calculates the RMS Voltage value from either the peak voltage, the peak-to-peak voltage, or the average voltage.

In many circuit applications, we encounter components connected together in one of two ways to form a three-terminal network: the “Delta,” or Δ (also known as the “Pi,” or π) configuration, and the “Y” (also known as the “T”) configuration. It is possible to calculate the proper values of resistors necessary to form one kind of network (Δ or Y) that behaves identically to the other kind, as analyzed from the terminal connections

Note: this is a very unique and useful property of e. As in the case of derivatives, the antiderivative of such a function is that same function. In the case of the antiderivative, a constant term “c” is added to the end as well.

Explain the difference between a balanced polyphase system and an unbalanced polyphase system. What conditions typically cause a polyphase system to become unbalanced?

If we connect a diode and resistor in series with a DC voltage source so that the diode is forward-biased, the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages as in Figure below (a). According to the “diode equation” here, the current through a forward-biased PN junction is proportional to e raised to the power of the forward voltage drop. Because

PARTS AND MATERIALS Four 6-volt batteries 12-volt light bulb, 25 or 50 watt Lamp socket High-wattage 12-volt lamps may be purchased from recreational vehicle (RV) and boating supply stores. Common sizes are 25 watt and 50 watt. This lamp will be used as a “heavy” load for your batteries (heavy load = one that draws substantial current). A regular household (120 volt) lamp socket will work just fine for these low-voltage “RV” lamps. CROSS-REFERENCES Lessons In

PARTS AND MATERIALS Automotive alternator (one required, but two recommended) Old alternators may be obtained for low prices at automobile wrecking yards. Many yards have alternators already removed from the automobile, for your convenience. I do not recommend paying full price for a new alternator, as used units cost far less money and function just as well for the purposes of this experiment. I highly recommend using a Delco-Remy brand

PARTS AND MATERIALS Low-voltage AC power supply (6 volt output) Four 1N4001 rectifying diodes (Radio Shack catalog # 276-1101) Small “hobby” motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) CROSS-REFERENCES Lessons In Electric Circuits, Volume 3, chapter 3: “Diodes and Rectifiers” LEARNING OBJECTIVES Design of a bridge rectifier circuit Advantages and disadvantages of the bridge rectifier circuit, compared to the center-tap circuit SCHEMATIC DIAGRAM ILLUSTRATION INSTRUCTIONS This circuit provides full-wave rectification without the

In addition to voltage and current, there is another measure of free electron activity in a circuit: power. First, we need to understand just what power is before we analyze it in any circuits. Power is a measure of how much work can be performed in a given amount of time. Work is generally defined in terms of the lifting of a weight against the pull of gravity. The heavier

Inductors do not have a stable “resistance” as conductors do. However, there is a definite mathematical relationship between voltage and current for an inductor, as follows: You should recognize the form of this equation from the capacitor chapter. It relates one variable (in this case, inductor voltage drop) to a rate of change of another variable (in this case, inductor current). Both voltage (v) and rate of current change (di

PARTS AND MATERIALS Low-voltage AC power supply (6 volt output) 6 volt battery One 1N4001 rectifying diode (Radio Shack catalog # 276-1101) Small “hobby” motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) Audio detector with headphones 0.1 µF capacitor (Radio Shack catalog # 272-135 or equivalent) The diode need not be an exact model 1N4001. Any of the “1N400X” series of rectifying diodes are suitable for the task, and they are quite easy