Vol 2: Electrical and Electronic Fundamentals Flashcards
Describe matter.
Any substance that has weight and takes up space.
What cannot be broken down into a simpler substance using ordinary chemical means?
Elements.
Define molecule.
The smallest part of a substance that has all the characteristics of that substance.
What are the elements that form molecules?
Atoms.
What type of charge does a proton carry? An electron?
Positive; negative.
When do we consider an atom to be electrically balanced?
When the negative charge of the electron is equal to the positive charge of the proton.
Provide a description of electrical current.
The uniform movement of electrons in a specific direction through a conductor (wire).
What is the term for an atom with eight electrons in the valence shell?
Stable or balanced atom.
What is an atom that has gained an electron called?
Negative ion.
What type of charge does a normal atom that has lost one electron have?
Positive.
The uniform movement of free electrons in a specific direction.
Current flow.
6.28 × 1018 electrical charges.
Coulomb.
One coulomb passing a given point per second.
Ampere.
Symbol for current used in equations.
I
Symbol for quantity of amperes.
A or a.
List four effects of current flow.
Heat, chemical change, magnetism, and physical shock.
Unit of measure for “electrical pressure.”
Volt.
The force which causes electrons to move from atom to atom.
Voltage or emf.
“E.”
Voltage.
Changes mechanical energy into electrical energy.
Generator.
Changes heat energy into electrical energy.
Thermocouple.
Unit of measure for all electrical opposition.
Ohm.
When 1 volt of pressure pushes 1 ampere of current flow through an electrical path, then 1 ohm
of resistance is present.
Ohm’s Law.
“R.”
Resistance.
Name four factors that affect resistance.
Any four of these: length, size, material, temperature, and reactance.
“W” or “P.”
Power
The rate of doing work.
Power
Unit in which electrical motors are rated.
Horsepower
Unit in which generators and regulators are rated.
Watts
Number of watts per horsepower.
746 Watts
What is magnetic material?
A material, usually iron, that has the ability to retain magnetic lines of force.
Define residual magnetism.
The induced magnetism that remains in a magnetic substance after we remove the magnetic field.
What materials do you use to make high-grade artificial magnets?
Aluminum, nickel, iron, and cobalt.
In what direction do the lines of force travel outside a bar magnet?
From the north pole to the south pole.
What action takes place when you place the south pole of one magnet near the south pole of
another?
They repel each other.
State the fundamental laws of magnetism.
Like poles repel each other; unlike poles attract.
When do magnetic lines of force cross?
Never.
What surrounds all current-carrying conductors?
Magnetic lines of force.
How can you strengthen the magnetic lines of force around a conductor?
By forming a number of loops close together.
What three items are necessary to have an electromagnet?
Coil of wire, core material, and current flow.
What type of core is preferred in the construction of relays and solenoids?
Soft iron core.
What is the relationship of the current to the voltage and resistance in a DC circuit according to
Ohm’s law?
The current in amperes is equal to the emf in volts divided by resistance in ohms.
Voltage = 90, current = 30, R = ?
3
Voltage = ?; current = 2; and resistance: R1 = 7, R2 = 5.
24
Voltage = 24; current = ?; resistance: R1 = 10, R2 = 8, R3 = 6.
1
What are the characteristics of resistance, current, and voltage in a DC-series circuit?
(1) The total resistance is the sum of the individual resistors.
(2) The same current flows in each part of the circuit.
(3) The applied voltage divides among the resistors according to their resistance.
What is the rule that pertains to the total current in a parallel circuit?
In a parallel circuit, the total current equals the sum of the current in the branches.
In solving for a value in a series-parallel circuit, what do you do to the circuit first?
Reduce a series-parallel circuit to an equivalent, simplified circuit. Replace each group of parallel resistors
with its equivalent single resistance; then, treat the entire circuit as a series circuit.
In your own words, define Kirchhoff’s voltage law.
The algebraic sum of the voltages around a closed loop must equal zero.
The ability to do work measured in joules.
Energy.
The production of motion against a resisting force measured in joules.
Work.
The rate of doing work measured in watts.
Power.
That which produces a change in motion of a body measured in dynes.
Force.
What formula do you use to compute power in a DC circuit when you only know resistance and
current?
P = I2R.
In a parallel circuit having four equal lamps, with an applied voltage of 120 volts and a total
current flow of 4 amperes, what is the power consumed at each lamp?
120 watts.
How do electrons travel in a circuit?
From negative to positive.
What is the difference in current flow between an AC circuit that contains only resistance and a
DC circuit that contains only resistance?
The current flow in a circuit containing resistance only is the same, regardless of whether the applied
voltage is AC or DC.
Explain Kirchhoff’s law for current as it applies to AC circuits.
AC circuits normally contain inductive and capacitive loads as well. Although they have different formulas
for determining their ohmic values, you can find their voltage and current values the same way as you did
by applying Kirchhoff’s laws for voltage and current in DC circuits.
In an AC circuit, when is the apparent power equal to the true power?
When the circuit consists of pure resistance.
When is the true power less than the apparent power?
When the current and voltage are out of phase due to reactance in the circuit.
What is the formula for power factor?
Power factor =100 watts (true power) / volts amps (apparent power)
A 240-volt AC motor records 35 in-line amperes. The in-line wattmeter shows only 7,600 watts
being consumed. What is the power factor of the AC circuit?
pf = 90.47, or 90.5 percent.
Name the portion of the applied power that produces the magnetic field in an AC circuit.
Wattless power or reactive power expressed in VARs.
What is the function of a generator?
To convert mechanical energy into electrical energy.
What are the types of alternators?
Single-phase and three-phase
In what two ways does an alternator operate?
By the principle of either moving conductors across a magnetic field or moving a magnetic field across the
conductors.
What are the operations of a single-phase alternator?
The first half revolution of the rotor produces a voltage in one direction and completes the first half of the
cycle; the second half revolution produces a voltage in the opposite direction and completes the last half of
the cycle.
What supplies the DC voltage in a three-phase alternator?
An exciter.
How many degrees are the poles set apart for three-phase operation of an alternator?
120
What is the difference between a primary and a secondary cell?
The primary cell can’t be recharged; the secondary cell can.
What solution is used for the electrolyte in a lead-acid battery?
Sulfuric acid and water solution.
What materials make up the negative and positive plates of a lead-acid battery?
The negative plate is spongy lead and the positive plate is lead peroxide.
What solution is used for the electrolyte in a nickel-cadmium battery?
Potassium hydroxide and distilled water.
What isolates instruments from high voltages or large currents?
Instrument transformers.
If the ratio of a transformer is 6 to 1 and the applied voltage to the primary is 120-VAC, what is
the voltage output from the secondary?
20 VAC
What causes voltage to be induced in a transformer?
Buildup and collapse of the current.
What does a transformer with a 1- to 2-turn ratio do to the voltage?
Step it up.
Name the main parts of a transformer.
Primary winding and secondary winding
What can you do to the secondary winding of a transformer to produce more than one voltage?
Center tap it.
Transistors have three leads. They are labeled E, B, and C, as follows:
- Emitter - Identified by diode symbol or arrow (Emits carriers).
- Base - Center electrode (controls flow).
- Collector- Unidentified electrode (Collects carriers).
Define the word electronics.
All applications involving the control of electricity using gasses or semiconductors.
What do we call the movement of free electons?
Current flow.
What are the two most common materials used to make semiconductors?
Germanium and silicon.
By what other term do we refer to a diode?
PN junction.
Is the N-type material of a diode the anode or cathode?
Cathode.
Is the P-type material of a diode the anode or cathode?
Anode.
What could happen if you do not observe polarity when connecting a diode?
You could unintentionally block current to a circuit.
Do electrons flow from cathode to anode or from anode to cathode?
Cathode to anode.
Which rating on a diode tells you the maximum voltage allowed in reverse bias?
PIV
Can we use a photo diode to trigger an LED?
No. (Although you can use an LED to trigger a photo diode.)
Name two applications for Zener diodes.
Voltage regulation and voltage limiting.
To what can we compare an SCR?
Latching relay.
A transistor may be connected in any one of three basic configurations:
- The common (grounded) emitter.
- The common (grounded) base.
- The common (grounded) collector
There are five major classes of circuit
components:
- Direct logic (DL).
- Resistor-transistor logic (RTL).
- Diode-transistor logic (DTL).
- Transistor-transistor logic (TTL).
- Direct-coupled transistor logic (DCTL).
What is the only difference between the symbols of the PNP and NPN transistors?
The direction of the arrow on the emitter lead.
In which direction does external current flow in a transistor?
Against the arrow on the emitter lead.
How do we show proper bias for a transistor on a schematic?
We use symbols to show proper bias polarities for the battery to the transistor.
What are the three basic configurations in which you can connect a transistor?
Common emitter; common base; and common collector.
To what is the grounded element common?
Both the input and output circuits.
What type of voltage is applied to a PNP transistor to satisfy the requirement for reverse bias
between the collector and base?
Negative voltage.
When testing an SCR or any other electronic devices, what precautions must you take?
Ensure that you know what voltage and current levels you are dealing with.
How can you vary or control the value of the forward breakover potential?
By applying an external signal at the control electrode (gate).
If you apply an AC signal to the anode, how can you make an SCR conduct during any portion of
the positive alternation?
By applying a portion of that positive signal to the gate.
How can an SCR be turned off in minimum time?
By reverse biasing the anode.
How does the gate of an SCR receive its signal?
A resistor is used as part of a voltage divider circuit.
How are most integrated circuits produced?
By a batch-fabrication method.
What are the changes in characteristics of integrated circuits that result from the differences in
manufacture and physical size?
1) Very few capacitors and almost no inductors are used.
(2) All voltages used are smaller than for discrete circuits.
(3) Component values tend to be smaller than for discrete circuits.
(4) Integrated circuit transistors normally will be NPN.
(5) Throw-away maintenance is used with integrated circuits.
How do you classify circuits that you use in digital equipment?
According to the types of components used in the circuit.
What are the five major classes of circuit components?
(1) Direct logic (DL).
(2) Resistor-transistor logic (RTL).
(3) Diode-transistor logic (DTL).
(4) Transistor-transistor logic (TTL).
(5) Direct-coupled transistor logic (DCTL).
What is one of the largest problems in integrated semiconductor operations?
Faulty connection between components and circuits.
Why is an integrated circuit a self-contained circuit?
It contains all required components.
How is half-wave rectification accomplished?
By placing a diode in series with a source of AC and a load resistor.
What does the application of AC cause that results in rectification?
A forward- and reverse-bias condition on a diode.
What is the unit of measure for the output ripple frequency of a half-wave rectifier?
Pulses per second (pps).
What is the operating characteristic of a full-wave rectifier?
It permits current to flow in the same direction through the load during both alternations of an AC input.
What are the identifying features of a full-wave rectifier?
Two diodes, a center-tapped transformer, and a load resistor.
Where is the output voltage of a full-wave rectifier developed?
Across the load resistor.
How much inverse voltage must each diode withstand in a full-wave rectifier?
An inverse voltage twice the value of the output peak voltage.
What must the breakdown rating be for diodes you use in a full-wave rectifier?
It must be twice as great as that of the half-wave diode.
How does the bridge rectifier design compare to that of the full-wave rectifier?
The bridge rectifier is a modified full-wave rectifier that may have either two or four diodes. Also, a bridge
rectifier does not have a center-tapped transformer.
Why are bridge and full-wave rectifiers considered full-wave devices?
Because current flows through the load resistor during both alternations of the input signal.
How does the peak output voltage from the bridge rectifier compare to that of the full-wave
rectifier?
The peak output voltage from the bridge is twice that of the full-wave.
What is the peak inverse voltage for bridge rectifier and full-wave rectifier circuits?
The PIV is the peak voltage applied across the entire secondary of the input transformer.
What can you use instead of a single-phase input when you need large amounts of power?
A three-phase input.
What is the phase angle between the three equal single-phase voltages of a three-phase generator?
120°.
What does current flow through the load produce in a three-phase bridge circuit?
Output polarity.
What is the three-phase, full-wave rectified output ripple frequency with a 60-hertz input?
360 pps.
How much filtering is needed to smooth DC output with low-amplitude ripple voltage?
Very little.
What is the purpose of a filter?
To convert pulsating DC to smooth DC.
Why does ripple voltage exist?
Because the rectifier supplies energy to the load in pulses.
How does a filter affect the ripple amplitude of the output of a rectifier?
Smoothes out the peak, or reduces the amplitude.
What is the relationship between the charge and discharge times a capacitive filter should have?
It should have a short charge time and a long discharge time.
What does the charge on a capacitor represent?
A storage of energy.
Once the capacitor is charged, when does the rectifier conduct?
It conducts when the input voltage to the rectifier exceeds the voltage across the capacitor.
How are capacitive filters connected with the load?
In parallel
What does the inductive filter use to provide filtering action?
The inductive reactance properties of the coil.
How are inductive filters connected to the load?
In series
What are the two types of L-type filters?
L-type inductor input filter and L-type capacitor input filter
What components make up an L-type filter?
An inductor and a capacitor.
When does the rectifier diode connected to the L-type filter in figure 3–21 conduct?
When the positive half of the incoming sine wave is applied to the transformer.
How much resistance is offered by the forward biased diode of an L-type filter?
Very little.
What happens as the positive half cycle of the L-type filter begins to decrease?
The diode approaches cutoff and the capacitor discharges through the load resistor.
Why is the output voltage across the load resistor high in the L-type capacitive input filter circuit?
Because the capacitor charges to the peak value of the L-type filter.
When you compare it to the capacitive input L-type filter, what does the inductive input L-type
filter provide?
It gives a lower output voltage and better voltage regulation.
What are the common characteristics of the two types of Pi-type filters?
Both of them have two capacitors to ground.
When you compare it to the RC Pi-type filter, what does the LC Pi-type filter provide?
It gives a high-output voltage and better voltage regulation.
In the transistor circuit, on what factors does the gain of the current, voltage, and power
amplifiers depend?
The alpha and beta values and the ratio of output to input resistance.
What factor enables a transistor to amplify?
A transistor can amplify because its middle electrode, the base, has an electrical advantage.
The input signal to the NPN transistor causes base current to change at the same rate as the input
signal, thus causing a change in transistor resistance. What does this change in resistance cause?
A relatively large voltage change.
In a common emitter configuration, what do we call resistor RL?
Collector load resistor.
What happens to base current, emitter current, and collector current during the negative
alternation of the input signal to a NPN common emitter amplifier?
They all decrease.
In the above question, what happens to the output that is taken from the collector with respect to
the emitter?
It is a voltage waveform that has the same characteristics as the input signal except that it has been enlarged
or amplified
What does the positive alternation of the input signal applied to the emitter of the NPN common
base amplifier cause?
The emitter current to decrease.
What is the controlling element in a common base configuration?
The emitter.
With a decrease in emitter and collector current, the voltage across the load resistor (RL)
decreases. What does this cause in a common base amplifier?
A positive output from collector to ground.
For the negative alternation of the input signal, the collector voltage varies at the same rate as the
input. What does this produce in a common base amplifier?
An amplified negative alternation.
What do we sometimes call a common collector amplifier configuration?
A grounded collector or emitter follower.
Where is the input signal applied and where is the output signal developed in a common collector
amplifier?
The input signal is applied between the base and ground. The output signal is developed between the
emitter and the ground collector. Thus, the collector is common to both input and output circuits.
What is degeneration?
The process of returning a part of the output of an amplifier to its input in such a manner that it cancels part
of the input signal.
What is the phase relationship between the input signal voltage and the output signal voltage of a
common or grounded emitter?
180° out-of-phase.
How is an electronic voltage regulator designed to operate?
It is designed to maintain the output voltage nearly constant regardless of input voltage or load changes.
How can you improve the operation of a simplified electronic voltage regulator?
By incorporating two class A amplifiers and a voltage divider network.
How can you change the output voltage of the electronic voltage regulator?
By moving the arm of the output voltage adjuster.
Are all AC-voltage waveforms sine waves?
No.
What is the most common frequency used for the transmission of electrical energy?
60 Hz in North America, 50 Hz in Europe, and 400 Hz in and around aircraft and air ground equipment.
What may high harmonic levels cause?
Interference to control and communication lines, heating of AC motors, higher reactive power demand and
hence poor power factor, misoperation of sensitive electronics, overloading of shunt capacitors, and higher
power loss.
What are the four purposes of harmonic measurements?
(1) Monitoring existing values of harmonics and checking against recommended or admissible levels.
(2) Testing equipment that generates harmonics.
(3) Diagnosis and trouble-shooting situations where the equipment performance is unacceptable to the
utility or to the US.
(4) Observations of existing background levels and tracking the trends in theme of voltage and current
harmonics (daily, monthly, seasonal patterns).
What kind of information does the display of the voltage waveform on the oscilloscope give?
Immediate qualitative information on the degree and type of distortion
How do spectrum analyzers display signals?
As a function of frequency
What do harmonic analyzers or wave analyzers measure?
The amplitude (and more complex units of the phase angles also) of a periodic function.
