Lesson 2a
T6A - Electrical components; fixed and variable resistors, capacitors, and inductors; fuses, switches, batteries
If you look at the printed circuit board of a modern piece of electronic equipment you can usually see several small items or components soldered to the board. Each component serves a purpose. An inductor can frequently be spotted because it is usually composed of a coil of wire.
Lesson one described EMF, Current, and Resistance and explained their relationship to each other. The current supplied by a voltage source can be opposed and thus controlled by a component with a predetermined resistance value known as a resistor. A fixed resistor does not have a means to change its value but variable resistors also known as potentiometer allows an operator or technician to change its resistance. Potentiometers are often used to control volume.
Do not become confused here. Both resistance and reactance oppose the flow of current but reactance only affects AC circuits and not DC. Resistance opposes the flow of current in a DC circuit
Two conductors in close proximity of each other but separated by an insulator have an ability to form an electric field that can store an electrical charge. When the surface area of the conductor is increased or the insulator that separates the conductors is made thinner the amount of energy that can be stored is increased if the voltage remains constant. This ability to store energy in the form of an electric field is called capacitance. A basic unit of capacitance is the farad. The electronic component that utilizes this phenomenon to provide a given level of capacitance to a circuit is called a capacitor.
Electrical energy can also be stored in a magnetic field. When a wire conducts an electrical current it forms a magnetic field around it. A wire wrapped in a coil allows each turn in the coil to interact with the other turns and thus compress the magnetic field it forms in a small area and store energy. The ability to store energy in a magnetic field is called inductance thus the coil of wire used to provide a given amount of inductance can be referred to an inductor or a coil. Inductance is measured in henrys.
A switch is used to connect and disconnect electrical circuits.
A fuse is designed to be the weakest link in an electrical circuit so if the current becomes excessive the fuse will open the circuit. By opening up when the current becomes too high the fuse protects other circuit components from current overloads.
A power source is necessary to operate any electronic device which included a ham radio. Mobiles and hand held radios normally use batteries as a power source. There are basically two types of batteries; the secondary cell which means it is rechargeable and primary cells which are considered not rechargeable. Carbon-zinc batteries are the most common primary cell batteries. Nickel-cadmium cells are secondary cells and a fully charged Nickel-cadmium cell will normally have a voltage of 1.2 volts.
*T6A01
What electrical component is used to oppose the flow of current in a DC circuit?
A. Inductor
B. Resistor
C. Voltmeter
D. Transformer
~~
*T6A02
What type of component is often used as an adjustable volume control?
A. Fixed resistor
B. Power resistor
C. Potentiometer
D. Transformer
~~
*T6A03
What electrical parameter is controlled by a potentiometer?
A. Inductance
B. Resistance
C. Capacitance
D. Field strength
~~
*T6A04
What electrical component stores energy in an electric field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A05
What type of electrical component consists of two or more conductive surfaces separated by an insulator?
A. Resistor
B. Potentiometer
C. Oscillator
D. Capacitor
~~
*T6A06
What type of electrical component stores energy in a magnetic field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A07
What electrical component is usually composed of a coil of wire?
A. Switch
B. Capacitor
C. Diode
D. Inductor
~~
T6A08
What electrical component is used to connect or disconnect electrical circuits?
A. Zener Diode
B. Switch
C. Inductor
D. Variable resistor
~~
*T6A09
What electrical component is used to protect other circuit components from current overloads?
A. Fuse
B. Capacitor
C. Shield
D. Inductor
~~
T6A10
What is the nominal voltage of a fully charged nickel-cadmium cell?
A. 1.0 volts
B. 1.2 volts
C. 1.5 volts
D. 2.2 volts
~~
T6A11
Which battery type is not rechargeable?
A. Nickel-cadmium
B. Carbon-zinc
C. Lead-acid
D. Lithium-ion
~~
Answers:
B, C, B, B, D, C, D, B, A, B, B
Lesson 2B
T6B – Semiconductors; basic principles of diodes and transistors
When I got my ham radio license, 1960, the most common active device used in amplifiers was the vacuum tube. (The term “active device” means the electronic component that uses voltage or current at the input to control the current flow at the output.) Transistor radios were just starting to become popular. Today the most common electronic components capable of using a voltage or current signal to control current flow is the transistor.
Semiconductors with special preparations make up the heart of modern solid state technology. Up to this point I have discussed conductors and insulators thus you may think a semiconductor is something that lies in between these two. The best way I know to explain a semiconductor is to say it is a conductor under certain conditions and an insulator under other conditions. Any greater explanation of semiconductors and how they work goes beyond the scope of these lessons and not necessary for you to know to get your Technician class license.
For now just accept that transistors, solid state diodes, Light Emitting diodes and other solid state components, not named here because they are not part of the test, are composed of treated semiconductors. There are two basic types of transistors: the bipolar junction transistor which is made of three layers of semiconductor material and the Field Effect Transistor abbreviated “FET”. For the purpose of the test remember that the bipolar transistor has an emitter electrode and the FET has a gate electrode.
Transistors can be used as an electronic switch or amplifier. The transistor is the main solid state component used as an amplifier.
The Diode allows current to flow in only one direction. The two elements of the diode are the “Anode” and the “Cathode.” A stripe on the body of the diode usually identifies the cathode side.
The Light Emitting Diode, abbreviated “LED”, will produce light while conducting current.
The input of an amplifier receives a signal then the amplifier processes it so a larger signal appears at the output. The ability of a transistor to amplify a signal is called “Gain.”
*T6B01
What class of electronic components is capable of using a voltage or current signal to control current flow?
A. Capacitors
B. Inductors
C. Resistors
D. Transistors
~~
*T6B02
What electronic component allows current to flow in only one direction?
A. Resistor
B. Fuse
C. Diode
D. Driven Element
~~
*T6B03
Which of these components can be used as an electronic switch or amplifier?
A. Oscillator
B. Potentiometer
C. Transistor
D. Voltmeter
~~
*T6B04
Which of these components is made of three layers of semiconductor material?
A. Alternator
B. Bipolar junction transistor
C. Triode
D. Pentagrid converter
~~
*T6B05
Which of the following electronic components can amplify signals?
A. Transistor
B. Variable resistor
C. Electrolytic capacitor
D. Multi-cell battery
~~
*T6B06
How is a semiconductor diode’s cathode lead usually identified?
A. With the word "cathode"
B. With a stripe
C. With the letter "C"
D. All of these choices are correct
~~
*T6B07
What does the abbreviation "LED" stand for?
A. Low Emission Diode
B. Light Emitting Diode
C. Liquid Emission Detector
D. Long Echo Delay
~~
*T6B08
What does the abbreviation "FET" stand for?
A. Field Effect Transistor
B. Fast Electron Transistor
C. Free Electron Transition
D. Field Emission Thickness
~~
*T6B09
What are the names of the two electrodes of a diode?
A. Plus and minus
B. Source and drain
C. Anode and cathode
D. Gate and base
~~
*T6B10
Which semiconductor component has an emitter electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B11
Which semiconductor component has a gate electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B12
What is the term that describes a transistor's ability to amplify a signal?
A. Gain
B. Forward resistance
C. Forward voltage drop
D. On resistance
~~
Answers:
D, C, C, B, A, B, B, A, C, A, B, A
LESSON 2c
T6C - Circuit diagrams; schematic symbols
The Technician class amateur radio license test may include some schematic symbol identification. Schematic symbols are standardized representations of components in an electrical wiring diagram. A schematic diagram gives an accurate representation of the way components are interconnected in an electrical circuit. It has nothing to do with the physical appearance of the components, the physical location of the components in the unit, or the wire lengths of components.
You do not need to learn how to actually read the diagrams but just how to identify a few individual components shown in the diagram.
There are four different components in diagram T1 which you may be asked to identify. Component 1 depicts a Resistor while component 2 is a Transistor. Component 3 of diagram T1 is a lamp and component 4 is a Battery.
The function of a transistor is to control the current. Section D has a question that refers to T1 and if you remember that a transistor controls current and that component 2 on the T1 drawing is a transistor you should score on that question if you get it.
Just look at them and try to remember what they look like. It might help to draw the individual components and label them.
Questions about four components from T2 appear in this section of the test question pool. They are as follows: component 6 is a Capacitor, component 8 is a light emitting diode, Component 9 shows a Variable Resistor, and component 4 is a Transformer.
Component 3 of T2 is a single-pole single-throw switch but that question will not appear until the next section.
Notice the similarity between component 1 in the T1 diagram and component 9 in the T2 drawing. They are both resistors but the arrow shows in component 9 of T2 identifies that the resistance is changeable or variable which makes it a variable resistor or potentiometer.
Diagram T3 only has two components to learn, component 3, the variable inductor (notice the arrow again which designates it as variable or changeable) and component 4 the antenna. (For information only and not on the test: Component 2 is a variable capacitor.)
*T6C01 (C)
What is the name for standardized representations of components in an electrical wiring diagram?
A. Electrical depictions
B. Grey sketch
C. Schematic symbols
D. Component callouts
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*T6C02 (A)
What is component 1 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Connector
~~
*T6C03
What is component 2 in figure T1?
A. Resistor
B. Transistor
C. Indicator lamp
D. Connector
~~
*T6C04
What is component 3 in figure T1?
A. Resistor
B. Transistor
C. Lamp
D. Ground symbol
~~
*T6C05
What is component 4 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Ground symbol
~~
*T6C06
What is component 6 in figure T2?
A. Resistor
B. Capacitor
C. Regulator IC
D. Transistor
~~
*T6C07
What is component 8 in figure T2?
A. Resistor
B. Inductor
C. Regulator IC
D. Light emitting diode
~~
*T6C08
What is component 9 in figure T2?
A. Variable capacitor
B. Variable inductor
C. Variable resistor
D. Variable transformer
~~
*T6C09
What is component 4 in figure T2?
A. Variable inductor
B. Double-pole switch
C. Potentiometer
D. Transformer
~~
T6C10
What is component 3 in figure T3?
A. Connector
B. Meter
C. Variable capacitor
D. Variable inductor
~~
T6C11
What is component 4 in figure T3?
A. Antenna
B. Transmitter
C. Dummy load
D. Ground
~~
T6C12
What do the symbols on an electrical circuit schematic diagram represent?
A. Electrical components
B. Logic states
C. Digital codes
D. Traffic nodes
~~
T6C13
Which of the following is accurately represented in electrical circuit schematic diagrams?
A. Wire lengths
B. Physical appearance of components
C. The way components are interconnected
D. All of these choices are correct
~~
Answers:
C, A, B, C, C, B, D, C, D, D, A, A, C
LESSON 2d
T6D - Component functions
Each component in an electronic circuit serves a specific purpose.
To provide the appropriate voltage for modern radio equipment the 120 VAC standard household power must be reduced significantly. A transformer can be used to reduce the AC voltage. Next the AC must be changed to DC because radios do not work directly on AC. A Rectifier changes alternating current into varying direct current signal. That varying direct current signal must be smoothed out but there are no questions in this section about components used to do that so I will not explain.
A regulator is used to control the amount of voltage from a power supply.
Switches are necessary to turn circuits on and off or to change the function of a circuit. Some switches are operated manually as the Single-pole single-throw switch like the one schematically drawn in Figure T2 item 3. Some switches are controlled by an electromagnet these switches are called relays.
Visual display of operation in electronic devices may be as simple as a light or group of lights. The LED is commonly used for this type of visual indicator. Other times the visual display requires a movement or meter. A meter can be used to display signal strength on a numeric scale.
Tuned circuits are the means of separating out specific frequencies of radio waves. That is how a radio receiver can select one station while rejecting others. A capacitor is used together with an inductor to make a tuned circuit.
A ham shack usually has the radios, transmitters and receivers, inside while the antennas are outside on some type of support. When the antenna and the radio are separated they need some form of feed-line or conductor to tie them together. Coaxial cable is commonly used to carry RF signals between a radio and antenna.
The function of a transistor controls the flow current in an electronic circuit. One question in this section refers to figure T1 component 2 which, as you learned earlier, represents a transistor. So it follows that component 2 in figure T1 controls the current.
In the 1960’s Integrated circuits (IC) began to show up in the field of electronics. An Integrated circuit is a way to combine several semiconductors and other components into one package.
*T6D01
Which of the following devices or circuits changes an alternating current into a varying direct current signal?
A. Transformer
B. Rectifier
C. Amplifier
D. Reflector
~~
*T6D02
What best describes a relay?
A. A switch controlled by an electromagnet
B. A current controlled amplifier
C. An optical sensor
D. A pass transistor
~~
*T6D03
What type of switch is represented by item 3 in figure T2?
A. Single-pole single-throw
B. Single-pole double-throw
C. Double-pole single-throw
D. Double-pole double-throw
~~
*T6D04
Which of the following can be used to display signal strength on a numeric scale?
A. Potentiometer
B. Transistor
C. Meter
D. Relay
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*T6D05
What type of circuit controls the amount of voltage from a power supply?
A. Regulator
B. Oscillator
C. Filter
D. Phase inverter
~~
*T6D06
What component is commonly used to change 120V AC house current to a lower AC voltage for other uses?
A. Variable capacitor
B. Transformer
C. Transistor
D. Diode
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*T6D07
Which of the following is commonly used as a visual indicator?
A. LED
B. FET
C. Zener diode
D. Bipolar transistor
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*T6D08
Which of the following is used together with an inductor to make a tuned circuit?
A. Resistor
B. Zener diode
C. Potentiometer
D. Capacitor
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*T6D09
What is the name of a device that combines several semiconductors and other components into one package?
A. Transducer
B. Multi-pole relay
C. Integrated circuit
D. Transformer
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*T6D10
What is the function of component 2 in Figure T1?
A. Give off light when current flows through it
B. Supply electrical energy
C. Control the flow of current
D. Convert electrical energy into radio waves
~~
*T6D11
Which of the following is a common use of coaxial cable?
A. Carry dc power from a vehicle battery to a mobile radio
B. Carry RF signals between a radio and antenna
C. Secure masts, tubing, and other cylindrical objects on towers
D. Connect data signals from a TNC to a computer
~~
Answers:
B, A, A, C, A, B, A, D, C, C, B
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