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# 3E051 Set C Book 2

Question | Answer |
---|---|

We call anything that has weight and occupies space | matter |

Scientists can combine elements in either | compounds or mixtures |

According to the elctron theory, atoms are composed of | protons, neutrons and electrons |

Which statement best describes a positive ion? | an atom that lost an electron and has more protons |

What effect of current causes an electric motor to produce mechanical energy? | Magnetism |

Which of there is the smallest current that can be fatal under certain conditions? | one-tenth of 1 amp |

What moves a sufficient number of electrons to perform a useful job? | voltage |

A thermocouple produces voltage as a result of what type of energy? | Heat |

According to Ohm's law, how much voltage is needed to push 1 ampere of current through 1 ohm of resistance? | 1 volt |

What normally causes the resistance of a conductor to increase? | increase in temperature |

What is the unit of measurement for electrical power? | watts |

A 3-horsepower motor consumes how much power? | 2.238 kW |

We call a magnet that is magnetized by induction from an external source | an artificial magnet |

You can create a polarity and increase the strength of the magnetic lines of force around a conductor by | looping the conductor into a coil |

What items are required to construct an electromagnet? | a coil of wire, a core material, and current flow |

What are the two most common methods of producing voltage? | chemical and mechanical |

What are the three things needed to produce voltage by the principle of eletromagnetic induction? | magnetic field, a conductor and relative motion |

What type of current flow is the result of voltages produced by batteries and thermocouples? | Direct current |

What type of current flow cannot be transformed from a higher voltage to a lower voltage? | Direct current |

Which formula for finding the resistance of a circuit is correct? | voltage divided by current |

What is the resistance of a circuit with an applied voltage of 120 volts and a curent flow of 9 amperes? | 13.33 ohms |

How much current flow is in a circuit that has 24 volts applied and 72-ohms of resistance? | 0.33 amperes |

What is the current flow in a series circuit with a 20-ohm resistor, a 25-ohm resistor, and a 30-ohm resistor connected to a 25-volt power supply? | 0.33 amperes |

The total current in a parallel circuit is equal to the | sum of the currents in the individual branches |

The joint resistance of a parallel circuit is equal to the applied voltage divided by the | total current |

What is the joint resistance of a 5-ohm resistor and a 20-ohm resistor in parallel? | 4 ohms |

What is the joint resistance of a 4-ohm resistor, a 10-ohm resistor and a 12-ohm resistor in parallel? | 2.3 ohms |

What is the current flow in amperes of a circuit with an applied voltage of 120 volts and a power consumption of 600 volts? | 5 amperes |

What is the power in watts consumed by a circuit with 120 volts applied and a resistance of 12 ohms? | 1200 watts |

How many watts of power are present in a 5-ohm unit of resistance through which 2 amperes are flowing? | 20 watts |

How many rotations per minute (rpm) must a 2-pole generator rotate to produce 60 Hz? | 3,600 rpm |

What do we call the actual rating of alternating current (AC) power that is available to do work? | effective value |

How do we express the measurement of the apparent power of an alternating current (AC) electrical system? | Kilovolt-amperes |

What unit of measurement do we use in calculating the induction of a coil? | Henry |

Which formula do we use to calculate impedance in an alternating current (AC) circuit? | Z=E/I |

What is the capacitance of a 125 microfarad capacitor when we convert it to farads? | 0.000125 F |

The rules and equations for direct current (DC) circuits apply to alternating current (AC) circuits having | only resistive load elements |

Kirchoff's voltage law states that | the algebraic sum around a closed loop must equal zero. |

In an alternating current (AC) circuit, when current and voltage are out of phase, true power is | less than apparent power |

A 110-volt alternating current (AC) motor records 20 in-line amperes, and the in-line wattmeter shows only 1,936 watts being consumed. What would be the power factor of the AC circuit? | 88 percent pf |

What type of generator has brushes riding on the commutator to carry the current to an external circuit? | DC circuit |

What is the advantage of a having rotating magnetic field alternator? | the output is taken from the stationary stator coils |

A three-phase alternator normally receives power for its rotating magnetic field from | a direct current (DC) generator |

The voltage of a primary cell depends on the type of | electolyte and the electrode material |

A step-up transformer produced a secondary voltage that is | higher and secondary current that is lower than the voltage and current in the primary |

What does the word electronics mean? | the control of electrons in motion |

An electron is considered a free electron when it reaches the | conduction band |

A positive mobile charge is considered a | hole |

What determines whether an element is a conductor, an insulator or a semiconductor? | the width of the forbidden band |

External heat applied to electronic components | causes increased current flow |

Which condition exists when you connect the negative battery lead to a cathode? | forward bias |

Which of the following shows a proper electronic relationship? | anode/p-type material |

Which device should only be used in direct current (DC) circuits? | Electrolytic capacitors |

What does the tapered side on some diodes indicate? | cathode |

Which meter connection do we use to read forward bias on a diode? | black lead to cathode |

What does the arrow on electronic components indicate? | The direction of hole current |

What is a zener diode typically used for? | voltage regulation |

What is the key to the silicon controlled rectifier's (SCR) operation? | gate |

How do we label the electrodes on a transistors? | Emitter, base, and collector |

Which of the following are types of transistors? | NPN and PNP |

How does the base of a transistor normally recieve its control voltage? | voltage divider circuit |

In how many configurations can we connect transistors? | three |

What controls the conduction time of a silicon controlled rectifier (SCR)? | gate current |

What components make up a voltage divider circuit? | resistors in series |

Which component protects a silicon controlled rectifier (SCR) gate from reverse voltage? | Diode |

How do you turn off a silicon controlled rectifier (SCR) in a minimum amount of time? | apply reverse bias to the anode |

The five major classes of integrated circuit components are direct logic (DL), transistor-transistor logic (TTL), | RTL, DTL, and DCTL |

Both discrete and integrated seiconductor operations share the common problem of | faulty connections |

Which of the following is a logic gate? | AND |

Which of the following is not a logic gate? | STOP |

The load resistor of a half-wave rectifier serves two purposes-to develop the output signal and to | limit current flow to a safe level |

A full wave rectifier can be identified easily because it contains | a center-tapped transformer |

The breakdown rating for diodes in a full-wave rectifier must be twice as great as the | half-wave rectifier |

The average output voltage level of a bridge rectifier is equal to 0.636 | peak input voltage |

The output ripple frequency (pps) of a three-phase bridge rectifier is how many times the input frequency | 6 times |

The output of a three-phase rectifier is of low amplitude and requires | little filtering |

In a circuit powered by a rectifier, why does a ripple voltage exist? | the rectifier supplies energy in pulses |

An inductive (choke) input filter gives a lower output voltage than the capacitive input LC filter and also provides | better voltage regulator |

Which statement describes the characteristics of the Pi-type LC filter in comparison to the RC pi-type filter? | High-output voltage and better voltage regulation |

In the common emitter configuration, the input is between the emitter and base, and the output is between the | collector and emitter |

If we apply the positive alternation of an input signal to the base of an NPN transistor in a common emitter configuration, what does it cause? | an increase in base current |

The controlling element element in a common base configuration is the | emitter |

Which gain characteristic of a common base transistor amplifier is less than 1? | current |

Input resistance to a common collector amplifier is high because the emitter signal opposes the | base signal |

What purpose does the zener diode in the elctronic voltage regulator serve? | sets the reference voltage |

The output voltage of the electronic voltage regulator circuit | can be adjusted to a specific value |

What are the most common frequencies for transmission of electrical power? | 50 Hz, 60 Hz, 400 Hz |

One effect of high harmonic levels is | misoperation of sensitive electronis |

Which three pieces of equipment do we use most often to measure harmonics? | wave analyzers, oscilloscope, spectrum analyzers |

Which piece of equipment gives immediate qualitative information on the degree and type of distortion? | oscilloscope |