Direct Current and Cell Types Quiz
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Questions and Answers

What is the unit of frequency?

  • Hertz (Hz) (correct)
  • Henry (H)
  • Joule (J)
  • Ohm (Ω)

    • What does the relationship $t = 1/f$ express?

  • The relationship between current and resistance.
  • The relationship between periodic time and frequency. (correct)
  • The relationship between energy and power.
  • The relationship between voltage and current.

    • Which type of current flows in one direction only?

  • Pulsating current
  • Alternating current (AC)
  • Direct current (DC) (correct)
  • Reactive current

    • What is the process called when an inductor induces a current in another nearby inductor?

    <p>Mutual inductance</p> Signup and view all the answers

    What does Lenz's law state regarding induced current?

    <p>It opposes the change in flux that produces it.</p> Signup and view all the answers

    What is the unit of inductance?

    <p>Henry (H)</p> Signup and view all the answers

    Which factors determine the electrical characteristics of an inductor?

    <p>Material of the core and physical dimensions</p> Signup and view all the answers

    What does Faraday's law indicate about induced electromotive force (emf)?

    <p>It depends on the relative velocity of the conductor cutting magnetic lines.</p> Signup and view all the answers

    What is the primary function of static dischargers or static wicks on an aircraft?

    <p>To dissipate static charge into the atmosphere</p> Signup and view all the answers

    Which materials are considered good conductors due to their high number of free electrons?

    <p>Aluminium and copper</p> Signup and view all the answers

    What typically protects static-sensitive devices from stray static charges?

    <p>Using wrist straps and grounding leads</p> Signup and view all the answers

    What happens to an atom when electrons are transferred between two materials?

    <p>The atom acquires a net positive or negative charge</p> Signup and view all the answers

    In a stable atom, how do the numbers of protons and electrons relate?

    <p>The number of protons and electrons is equal, making the atom neutral</p> Signup and view all the answers

    What unit is commonly used to measure electrostatic charge for practical purposes?

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

    What is a free electron in a conductive material?

    <p>An electron that can move freely within the material</p> Signup and view all the answers

    What characteristic of materials makes them suitable as insulators?

    <p>Low number of free electrons</p> Signup and view all the answers

    What factors influence the magnitude of the induced e.m.f. in a conductor?

    <p>Strength of the magnetic field</p> Signup and view all the answers

    What is the relationship between power and energy in an electrical system?

    <p>Power is the rate at which energy is converted.</p> Signup and view all the answers

    What occurs when a conductor cuts through a magnetic field at right angles?

    <p>An e.m.f. is induced.</p> Signup and view all the answers

    Which of the following best describes ferromagnetic materials?

    <p>They demonstrate strong magnetic properties like iron.</p> Signup and view all the answers

    In electromagnetic induction, what is required to generate electricity?

    <p>Movement in conjunction with a magnetic field and a closed conductor.</p> Signup and view all the answers

    What does the unit of energy, the joule (J), represent?

    <p>The capacity to do work</p> Signup and view all the answers

    When the angle between a conductor and magnetic field lines is 90°, what effect does it have on induced e.m.f.?

    <p>It maximizes the induced e.m.f.</p> Signup and view all the answers

    How is the magnetic field of a conductor described?

    <p>It spreads out around the conductor in concentric circles.</p> Signup and view all the answers

    What is the main difference between primary cells and secondary cells?

    <p>Primary cells produce electricity from chemicals used up, while secondary cells convert energy back into chemicals.</p> Signup and view all the answers

    What is essential to observe when removing and replacing aircraft batteries?

    <p>The manufacturer's guidelines for correct isolation must be followed.</p> Signup and view all the answers

    How can the strength of an electric field be defined?

    <p>Proportional to the applied potential difference and inversely proportional to distance.</p> Signup and view all the answers

    What characterizes the interaction between charged bodies with the same polarity?

    <p>They repel each other.</p> Signup and view all the answers

    What causes static electricity in insulators?

    <p>The separation of electrons and protons due to rubbing two materials.</p> Signup and view all the answers

    What phenomenon is indicated by the electric field created between charged parallel metal plates?

    <p>Capacitance storage.</p> Signup and view all the answers

    What happens to static charges over time in insulating materials?

    <p>They eventually dissipate due to dielectric losses.</p> Signup and view all the answers

    What is the primary aim of managing static electricity on an aircraft?

    <p>To equalize the potential of all points on the aircraft's surfaces.</p> Signup and view all the answers

    What happens to an atom when it loses electrons?

    <p>It becomes a positive ion.</p> Signup and view all the answers

    According to Kirchhoff's voltage law, what is the relationship of potential drops in a closed network?

    <p>The sum is equal to zero.</p> Signup and view all the answers

    What does Ohm's law state about the relationship between current and voltage in a conductor?

    <p>Current is directly proportional to voltage.</p> Signup and view all the answers

    In the formula $I = \frac{Q}{t}$, what does 'I' represent?

    <p>Current.</p> Signup and view all the answers

    What is the unit of resistance?

    <p>Ohm.</p> Signup and view all the answers

    What does the electromotive force (e.m.f.) create in a circuit?

    <p>Current flow.</p> Signup and view all the answers

    If a steady current of 3A flows for two minutes, how much charge is transferred?

    <p>180 Coulombs.</p> Signup and view all the answers

    Which statement describes the relationship between voltage and charge according to the formula $V = \frac{W}{Q}$?

    <p>Voltage is the energy required to move charge.</p> Signup and view all the answers

    Study Notes

    Frequency and Periodic Time

    • Frequency measures how many cycles of a waveform occur in one second, expressed in hertz (Hz).
    • Periodic time (or period) is the duration of one complete cycle of the waveform.
    • Relationship: t = 1/f or f = 1/t.

    Alternating Current vs. Direct Current

    • Direct current (DC) flows in one direction only, whereas alternating current (AC) reverses direction periodically.
    • Waveforms graphically represent voltage or current variations in AC circuits.

    Inductors

    • Inductors store electrical energy in a magnetic field, utilized in chokes, filters, and selective circuits.
    • The electrical properties of inductors depend on core material, coil turns, and physical dimensions.

    Self-Inductance and Mutual Inductance

    • Mutual inductance occurs when a changing current in one inductor induces a current in another close inductor.
    • Self-inductance (L) refers to a back electromotive force generated by changes in current, measured in henries (H).

    Faraday's and Lenz's Laws

    • Faraday's law states that the induced electromotive force (emf) depends on how quickly the conductor cuts magnetic flux lines.
    • Lenz's law indicates that the induced current opposes the change in magnetic flux that produces it.

    Electromagnetic Induction

    • The generated electromotive force (emf) relates to the conductor's length, magnetic field strength, and relative velocity.
    • Electricity generation requires movement of a closed conductor within a magnetic field.

    Electromagnetism and Inductors

    • A magnetic field is the area around a magnet where magnetic forces are exerted; it surrounds a conductor carrying an electric current.
    • Ferromagnetic materials (like iron, nickel, and cobalt) have strong magnetic properties and react significantly to external magnetic fields.

    Power and Energy

    • Power (P), measured in watts (W), is the rate of energy conversion, defined as P = W/t.
    • Energy is the capacity to do work, measured in joules (J). It can be transformed between forms.
    • Primary cells are non-rechargeable, while secondary cells can be recharged through reversible chemical reactions.

    Direct Current Safety

    • Follow Aircraft Maintenance Manual (AMM) guidelines for isolating batteries before removal or replacement in aircraft.

    Electric Field

    • An electric field is the force region around a charged particle, defining the direction and magnitude of the force on other charges.
    • Between two parallel plates, the electric field strength (E) depends on applied potential difference and plate distance.

    Electrostatics and Capacitors

    • Like charges repel, while opposite charges attract; static electricity can build from friction and may need to be dissipated in aircraft.
    • Stray static charges can damage sensitive devices; proper ESD precautions include wrist straps and grounded packaging.

    Electron Theory

    • Charge value is expressed in coulombs. Conductors (e.g., copper, aluminum) have many free electrons that allow current flow.
    • Electrons can be detached from atoms, creating positive or negative ions, which result in electrostatic effects.

    Kirchhoff's Laws

    • Kirchhoff's Current Law: Total current at a junction is zero.
    • Kirchhoff's Voltage Law: The sum of potential drops in a closed circuit is zero.

    Ohm's Law

    • Current (I) is directly proportional to voltage (e.m.f.) and inversely proportional to resistance (R).
    • The basic circuit includes a voltage source (battery) and a load (resistor).

    Current, Voltage, and Resistance

    • Current (I), measured in amperes (A), is the flow rate of charge (1 A = 1 coulomb/second).
    • Voltage (V) is the electromotive force that drives current flow, defined as the energy per charge (1 V = 1 J/C).
    • Resistance (R), measured in ohms (Ω), is the opposition to charge flow caused by collisions within the material.

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    Description

    Test your knowledge on primary and secondary cells in direct current systems. This quiz will explore the chemical processes involved in energy conversion, including the differences between non-rechargeable and rechargeable cells. Understand the principles behind electrical energy generation and storage.

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