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principles - grol
48 questions
| Question | Answer |
|---|---|
| The product of the readings of an ac meter and ac ammeter is called: | Apparent power |
| What is the basic unit of electrical power? | Watts |
| What is the term to express the amount of electrical energy stored in an electrostatic field? | Joules |
| What device is used to store electrical energy in an electrostatic field? | Capacitor |
| What formula would determine the inductive reactance of a coil if frequency and coil inductance is known? | XL = 2 (3.14) fl |
| What is the term for the out of phase power associated with inductors and capacitors? | Reactive power |
| What determines the strength of the magnetic field around A conductor? | The amount of current |
| What will produce a magnetic field? | A current flowing through a conductor |
| When induced currents produce expanding magnetic fields around conductors in a direction That opposes the orignal magnetic field, this known as: | lenz's law |
| The opposition To the creation of magnetic lines of force in a magnetic circuit is known as: | reluctance |
| What is meant by the term "back EMF" ? | A voltage that opposes the applied EMF |
| Permeability is defined as: | the ratio of magnetic flux Density in a substance to the magnetizing force that produces it. |
| What metal is usually employed as a sacrifical anode for corrosion control purposes? | Zinc bar |
| What is the relative dielectric constant for air? | 1 |
| Which metal object May be least affected by galvanic corrosion when submerged in seawater? | Stainless steel propeller shaft |
| Skin effect is the phenomenon where: | RF current flows in a thin layer of the conductor, closer to the surface, as frequency increases. |
| Corrosion resulting from electric current flow between dissimilar metals is called: | Galvanic Corrosion |
| Which of these will be most useful for insulation at UHF frequencies? | Mica |
| What formula would calculate the total inductance of inductors in series? | Lt= l1+l2+l3...ln |
| Good conductors with minimum resistance have what type of electrons? | Many free electrons |
| Which of the 4 groups of metals listed below are the best low-resistence conductors? | Gold, silver, and copper |
| What is the purpose of a bypass capacitor? | It removes alternating current providing a low impedance path to ground. |
| How would you calculate the total capacitance of three capacitors in parallel ? | Ct=c1+c2+c3 |
| How might you reduce the inductance of an antenna coil? | Reduce the number of turns |
| What are the two most commonly used specifications for a junction diode? | Maximum forward current and piv (peak inverse voltage) |
| What are the limits the maximum forward current of a Junction diode? | The junction temperature |
| MOSFETs aee manufactured with THIS protective device built into their gate to protect the device from static charge and excessive voltages: | zener diode |
| What are the two basic types of junction field effects transistors? | N-channel and p-channel |
| A common emitter amplifier has: | More voltage gain than a common collector |
| How does the input impedance of a field-effect transistor compare with that of a biopolar transistor? | A FET has high input impedance ; a bipolar transistor has low input impedance. |
| An ac ammeter indicates: | effective (rms) values of current. |
| By what factor must the voltage of an ac circuit , as indicated on the scale of an ac voltmeter, be multiplied to the peak voltage value? | 1.414 |
| What is the rms voltage at a common household electric power outlet? | 117-v ac |
| What is the easiest voltage amplitude to a measure by viewing a pure sine wave signal on an oscilloscope? | Peak to peak |
| By what factor must voltage measured in an ac circuit, as indicated on the scale of am ac voltmeter, be multiplied to obtain the average voltage value? | 0.9 |
| What is the peak voltage at a common household electrical outlet? | 165.5 volts |
| What is a sine wave ? | A wave whose amplitude at any given instant can be represented by the projection of a point on a wheel rotating uniform speed. |
| How many degrees are there in one complete sine wave cycle? | 360° |
| What type of wave is made up of sine waves of the fundamental frequency and all odd harmonics? | Square |
| what is the description of a square wave? | A wave that abruptly changes back and forth between two voltage levels and stays at these levels for equal amount of time. |
| What type of wave is made up of sine waves at the fundamental frequency and all the harmonics? | Sawtooth wave |
| What type of wave is characterized by a rise time significantly faster than the fall time (or vice versa)? | Sawtooth wave |
| What is the term used to identify an ac voltage that would cause the same heating in a resistor as a corresponding value of dc voltage? | Root mean square (rms) |
| What happens to reactive power in a circuit that has both inductors and capacitors? | It alternates between magnetic and electric fields and is not dissipate. |
| Halving the cross-sectional area of a conductor will: | double the resistance |
| Which of the following groups is correct for listing common materials in order of decending conductivity? | Silver, copper, aluminum, iron, lead |
| How do you compute true power (power dissipated in the circuit) in a circuit where ac voltage and current are out of phase? | Multiply apparent power times power factor . |
| Assuming a power source to have a fixed value of internal resistance, maximum power will be transferred to the load when: | the load impedance equals the internal impedance of the source |
Created by:
pookee888
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