CASA Part 66 - B-03a Electrical Fundamentals Quiz
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Questions and Answers

What is the key to Edison's explanation of thermionic emission in the light bulb?

  • The small space between the filament and plate
  • The high temperature of the conductor
  • The vacuum inside the bulb
  • The positive charge on the plate attracting the negative electrons (correct)

    • What would happen if the electrons had to be forcibly pulled from a cold filament?

  • The electrons would destroy the filament (correct)
  • The plate would be negatively charged
  • The vacuum inside the bulb would be compromised
  • The flow of electrons would increase

    • Which term is used to describe the process of free electrons boiling from the conductor's surface?

  • Thermionic emission (correct)
  • Electron escape
  • Steam emission
  • Conductor agitation

    • What effect does the temperature of the conductor have on the free electrons?

    <p>It increases their speed and agitation</p> Signup and view all the answers

    Why did Edison's bulb have a vacuum inside?

    <p>To allow electrons to flow without burning the filament</p> Signup and view all the answers

    What is the measure of the voltage between two bodies with different potentials?

    <p>The potential difference (PD)</p> Signup and view all the answers

    In a circuit with steady EMF, what happens to the current if the resistance is doubled?

    <p>The current halves</p> Signup and view all the answers

    What is the unit of electrical resistance?

    <p>Ohm (Ω)</p> Signup and view all the answers

    How does resistance change in relation to the length of a conductor?

    <p>Resistance is directly proportional to the length</p> Signup and view all the answers

    What is the measure of the potential difference (PD) between two bodies?

    <p>Measurable voltage between the bodies</p> Signup and view all the answers

    What happens to the resistance of most materials as their temperature increases?

    <p>The resistance increases</p> Signup and view all the answers

    What is the reciprocal of resistance called?

    <p>Conductance</p> Signup and view all the answers

    If a material has a conductance of 2 siemens, what is its resistance?

    <p>0.5 ohms</p> Signup and view all the answers

    How can the relationship between voltage, current, and resistance be described?

    <p>$V = IR$</p> Signup and view all the answers

    What is the major cause of static electricity according to the triboelectric effect?

    <p>Friction and pressure</p> Signup and view all the answers

    What determines the magnitude of the static charge according to the text?

    <p>Material composition and separation rate</p> Signup and view all the answers

    How does humidity influence the level of electrostatic charges?

    <p>Low humidity generates higher static charges</p> Signup and view all the answers

    In what conditions does static become more noticeable according to the text?

    <p>Winter months, dry climates, and air-conditioned environments</p> Signup and view all the answers

    How does increasing humidity to 60% affect static build-up according to the text?

    <p>It limits static build-up</p> Signup and view all the answers

    What is the defining characteristic of an insulator in terms of the number of free electrons in its valence shell?

    <p>5-8 free electrons</p> Signup and view all the answers

    Why are rubber and its variants commonly used as insulators around copper wiring?

    <p>The electrons are tightly bound within the material</p> Signup and view all the answers

    What is the defining characteristic of a semiconductor in terms of the number of free electrons in its valence shell?

    <p>2-4 free electrons</p> Signup and view all the answers

    Which material is mentioned as a common semiconductor compound?

    <p>Gallium arsenide (GaAs)</p> Signup and view all the answers

    Why are semiconductors considered extremely useful in electronics?

    <p>They can act as both insulator and conductor</p> Signup and view all the answers

    According to the triboelectric series, what can be predicted about the voltage levels generated when two materials are rubbed together?

    <p>Materials close together in the series will produce less voltage than those further apart in the series</p> Signup and view all the answers

    What is the relationship between the materials' position on the triboelectric series and their charge?

    <p>Materials higher on the series become positively charged, while those lower become negatively charged</p> Signup and view all the answers

    What did Coulomb's Law of Charges discover and write about in the 1780s?

    <p>The relationship between attracting or repelling charged bodies</p> Signup and view all the answers

    What can be inferred about electrostatic voltages at different relative humidities from the given table?

    <p>Voltages decrease as relative humidity increases</p> Signup and view all the answers

    What does a worker at a bench generate in terms of electrostatic voltage, according to the given table?

    <p>6,000 volts</p> Signup and view all the answers

    Which material is the best conductor of electricity according to the text?

    <p>Gold</p> Signup and view all the answers

    In terms of conductivity, which material comes after copper?

    <p>Gold</p> Signup and view all the answers

    What is the most common conductor used in electrical cable according to the text?

    <p>Copper</p> Signup and view all the answers

    Which material is used only in special applications due to its high cost?

    <p>Silver</p> Signup and view all the answers

    What is commonly used as a baseline by which to compare other materials' resistance?

    <p>Copper</p> Signup and view all the answers

    Which metal is the best conductor out of silver, copper, gold, aluminium, brass, and carbon?

    <p>Silver</p> Signup and view all the answers

    Why are silver and gold used only in special applications as conductors?

    <p>Due to their high cost</p> Signup and view all the answers

    What is commonly used as the baseline for comparing the resistance of other conducting materials?

    <p>Copper</p> Signup and view all the answers

    In which industry might steel, aluminium, and other metals be used as conducting mediums?

    <p>Automobile industry</p> Signup and view all the answers

    What is resistivity commonly referred to as?

    <p>Resistance</p> Signup and view all the answers

    Which material is commonly used as the baseline for comparing other materials' resistance?

    <p>Copper</p> Signup and view all the answers

    What determines the common focus on conductors' and components' resistance?

    <p>Resistance</p> Signup and view all the answers

    What is the descending order of conductivity among silver, copper, gold, aluminium, brass, and carbon?

    <p>$Silver &gt; Copper &gt; Gold &gt; Aluminium &gt; Brass &gt; Carbon$</p> Signup and view all the answers

    'Many are rarely produced specifically as conductors' refers to which kind of materials?

    <p>'Metals'</p> Signup and view all the answers

    What is the most common conductor used in electrical cable?

    <p>Copper</p> Signup and view all the answers

    Study Notes

    Thermionic Emission and Edison's Light Bulb

    • Edison's explanation of thermionic emission involves free electrons escaping from a heated filament.
    • Forcibly pulling electrons from a cold filament would require significant energy, leading to inefficient and impractical operation.
    • The process of free electrons boiling from a conductor’s surface is termed "thermionic emission."
    • Higher temperatures of the conductor increase the number of free electrons available for conduction.

    Bulb Design and Electrical Properties

    • Edison's light bulb contained a vacuum to prevent oxidation and prolong filament lifespan.
    • The voltage between two bodies with different potentials is measured in volts (V).
    • In a constant EMF circuit, if resistance is doubled, the current is halved according to Ohm's law.
    • The unit of electrical resistance is ohm (Ω).

    Resistance and Conductor Characteristics

    • Resistance increases with the length of a conductor, following the principle that longer conductors impede current flow more than shorter ones.
    • The measure of potential difference (PD) between two bodies is also in volts (V).
    • For most materials, resistance increases as temperature rises due to increased lattice vibrations that impede electron flow.
    • The reciprocal of resistance is called conductance, measured in siemens.

    Conductance and Voltage Relationships

    • A material with a conductance of 2 siemens has a resistance of 0.5 ohms.
    • The relationship between voltage (V), current (I), and resistance (R) can be described by Ohm's Law: V = I × R.

    Static Electricity and Humidity Effects

    • The major cause of static electricity is the triboelectric effect, where materials become charged through friction.
    • The magnitude of the static charge depends on the types of materials and their surface conditions.
    • High humidity levels reduce static charges because moisture allows charge dissipation.
    • Static becomes more noticeable in dry environments, where humidity is low.
    • Increasing humidity to 60% significantly reduces static build-up by enhancing moisture content in the air.

    Insulators, Semiconductors, and Conductors

    • Insulators have few free electrons in their valence shell, preventing electrical conduction.
    • Rubber and its variants are used as insulators due to their ability to block electron flow while being flexible.
    • Semiconductors have a moderate number of free electrons allowing controlled conductivity.
    • Silicon is a common semiconductor compound due to its favorable electronic properties.

    Electrical Charge Characteristics

    • The triboelectric series predicts voltage levels generated when two materials are rubbed together based on their relative electron affinity.
    • Materials higher on the series tend to lose electrons and become positively charged, whereas those lower gain electrons and become negatively charged.
    • Coulomb's Law of Charges, discovered in the 1780s, describes the force between charged objects based on their charges and distances apart.

    Conductivity and Material Comparisons

    • A worker at a bench can generate electrostatic voltages significantly higher at low humidity levels as per electrostatic tables.
    • Silver is the best conductor of electricity, with copper following close behind.
    • The most common conductor used in electrical cables is copper, while gold and silver are reserved for special applications due to their high costs.
    • The baseline for comparing resistance of conducting materials is often copper.

    Industry and Application Considerations

    • Steel, aluminum, and other metals are used as conductors in various industries such as construction and manufacturing.
    • Resistivity is commonly referred to as a material's inherent opposition to current flow.
    • The common focus on resistance in conductors and components usually concerns performance efficiency in applications.
    • The descending order of conductivity among silver, copper, gold, aluminum, brass, and carbon prioritizes silver, followed by copper, demonstrating their effectiveness as conductors.

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    CASA B-03a Electrical Fundamentals I PDF

    Description

    Test your knowledge on means of static generation and electrostatic voltages at different relative humidities with this quiz based on page 31 of training materials for CASA Part 66. Explore scenarios like walking across different surfaces and handling various objects to understand electrostatic voltages.

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