DC vs AC Current Quiz
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Questions and Answers

Which statement about Direct Current (DC) is true?

  • It has a fixed polarity. (correct)
  • It reverses polarity continuously.
  • It is easier to amplify than Alternating Current.
  • It varies in magnitude frequently.

    • What defines a Closed Circuit?

  • Current divides between multiple paths.
  • Provides a pathway for current only under certain conditions.
  • Incomplete and disconnected path.
  • Current flows uninterrupted through all components. (correct)

    • In a Series Circuit, what happens to the current if one component fails?

  • The circuit will reroute the current around the failed component.
  • All components continue to function.
  • The current can still flow through other components.
  • The current stops entirely. (correct)

    • Which statement is accurate about Parallel Circuits?

    <p>They ensure that other components continue working if one fails.</p> Signup and view all the answers

    What is a characteristic of a Short Circuit?

    <p>It may lead to overheating and fires.</p> Signup and view all the answers

    Which of the following statements about Alternating Current (AC) is true?

    <p>AC voltage can be stepped up or down.</p> Signup and view all the answers

    What distinguishes an Open Circuit from a Closed Circuit?

    <p>An Open Circuit is incomplete and disconnected.</p> Signup and view all the answers

    Why are circuit breakers and fuse boxes important?

    <p>They cut off current as a safety measure during faults.</p> Signup and view all the answers

    What is the primary function of a battery?

    <p>To store and supply direct current through electrochemical means</p> Signup and view all the answers

    Which type of battery is known as rechargeable?

    <p>Secondary Batteries</p> Signup and view all the answers

    What type of electrical energy do alternating current generators produce?

    <p>Alternating current electricity</p> Signup and view all the answers

    What is the main use of direct current generators?

    <p>To supply electrical energy for elevators and telecommunications</p> Signup and view all the answers

    What is a dynamo specifically known for creating?

    <p>Direct current using a commutator</p> Signup and view all the answers

    What characteristic differentiates primary batteries from secondary batteries?

    <p>Primary batteries can deliver electricity immediately upon assembly</p> Signup and view all the answers

    Which of the following statements is true about generators?

    <p>Generators convert mechanical energy to electrical energy</p> Signup and view all the answers

    What is the foundational role of dynamos in electrical generation?

    <p>They were the first to deliver power for various applications</p> Signup and view all the answers

    What is the main advantage of using Alternating Current (AC) over Direct Current (DC) for power distribution?

    <p>AC is more efficient in transporting over long distances.</p> Signup and view all the answers

    Which statement about Direct Current (DC) is true?

    <p>DC is best suited for devices powered by batteries.</p> Signup and view all the answers

    What defines one complete Cycle of Alternating Current (AC)?

    <p>The flow of current from maximum to zero to negative maximum and back to zero.</p> Signup and view all the answers

    Why is it important to convert Alternating Current (AC) to Direct Current (DC) in rechargeable devices?

    <p>DC is more stable for battery operation.</p> Signup and view all the answers

    What is the typical frequency used for lighting in households powered by AC?

    <p>60 Hertz</p> Signup and view all the answers

    Which of the following appliances is likely powered by Alternating Current (AC)?

    <p>Electric toaster</p> Signup and view all the answers

    Which type of electric current is characterized by a consistent direction and is used in batteries?

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

    What is meant by the term 'phasing' in the context of Alternating Current (AC)?

    <p>The number of currents being distributed simultaneously.</p> Signup and view all the answers

    What type of machine converts electrical energy to mechanical energy?

    <p>Electric Motor</p> Signup and view all the answers

    Which of the following materials is considered a good conductor of electricity?

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

    What does a step-up transformer do?

    <p>Increases voltage</p> Signup and view all the answers

    Which of the following is NOT a property of insulators?

    <p>Have free electrons</p> Signup and view all the answers

    Which unit is used to measure electric charge?

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

    What is the main purpose of conductors in electrical systems?

    <p>To allow current to flow</p> Signup and view all the answers

    Which of the following best describes a rotary converter?

    <p>A device for converting alternating current to direct current</p> Signup and view all the answers

    Which material is known to provide the highest resistivity and act as an insulator?

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

    What is the relationship described by Ohm's Law?

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

    Which unit measures electrical resistance?

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

    How is the current (I) calculated using resistance (R) and voltage (V)?

    <p>I = V/R</p> Signup and view all the answers

    Which statement about electric power (W) is correct?

    <p>Power is calculated by multiplying current by voltage.</p> Signup and view all the answers

    What does ampacity refer to?

    <p>The current carrying capacity of a wire or cable.</p> Signup and view all the answers

    Which of the following represents one coulomb?

    <p>The flow of approximately 6.25 x 10^18 electrons per second.</p> Signup and view all the answers

    Which unit measures electric potential difference?

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

    Which equation identifies the electrical power in terms of voltage and resistance?

    <p>W = I^2R</p> Signup and view all the answers

    Study Notes

    Direct Current (DC)

    • Uniform in strength
    • Batteries are a common example.
    • Used in electronic devices with a battery power source.
    • Used to charge batteries in rechargable devices like laptops and cell phones.
    • Two types: Continuous and pulsating

    Alternating Current (AC)

    • Reverses direction
    • Current periodically varies in time rate and direction
    • Frequency: cycles per second or Hertz
      • Lighting: 60 Hertz
      • Motors: 25 Hertz
    • Phasing: Single Phase or 3-phase
    • Most households and offices use AC because it loses less power than DC and has fewer issues converting high voltage to low voltage using transformers
    • AC can be transported over long distances
    • Powers electric motors which power household appliances like fridges, dishwashers, and toasters.
    • Also powers things connected to the mains like TVs or chargers for laptops and phones.

    Direct Current (DC) vs. Alternating Current (AC)

    • DC:
      • Fixed polarity
      • Steady or fluctuating
      • Steady value
      • Easier to measure: 1.5 volts
    • AC:
      • Reverses polarity
      • Varies between reversals
      • Stepped up or down
      • Easier to amplify: 110V+

    Electrical Circuits

    • A complete conducting path carrying current from a source of electricity to and through some electrical device or load and back to the source.
    • Types of circuits:
      • Closed Circuit: complete, continuous path
      • Open Circuit: broken, incomplete, disconnected (non-functional)
      • Series Circuit: same current flows through all components, current has only one path to take.
      • Parallel Circuit: components are arranged so that the current divides between them.
      • Short Circuit: condition resulting from bridging any part of a circuit with a conductor of very low resistance. Can cause wires to heat up and potentially cause fire.

    Sources of Electricity

    • Battery: Combination of two or more electric cells capable of storing and supplying direct current by electrochemical means.
      • Primary Batteries: Deliver electricity as soon as its parts are assembled, non-renewable.
      • Secondary / Storage Batteries: Electricity from some external source must pass through before it can deliver electric current. Used for emergency lighting, rechargeable.
    • Generator: Machine which converts mechanical energy to electrical energy.
      • Alternating Current Generators / Alternators: Converts mechanical energy to electrical energy in the form of alternating current.
      • Direct Current Generators: Rotating machine that supplies electrical output with unidirectional voltage and current. Used for elevators, escalators, telecommunications, signal systems, and clock systems.
    • Dynamo Electric Machines: Electrical generator that creates direct current using a commutator
      • Motors: machine that converts electrical energy to mechanical energy
      • Transformers: Machine for converting one voltage to another. Step-up transformer increases voltage, step-down transformer decreases voltage.
      • Rotary Converters: Changing alternating current to direct current and vice versa.

    Conductors

    • Materials or substances which allow electricity to flow through them.
    • Humans and animals are conductors.
    • Have free electrons on its surface which allow current to pass through easily.
    • Transmit heat or light from one source to another.
    • Examples: Copper, Brass, Steel, Gold, and Aluminum

    Insulators

    • Materials or substances which resist or don’t allow the current to flow through them.
    • Do not have free electrons.
    • Examples: Wood, cloth, glass, mica, quartz, plastic, rubber

    Unit of Quantity

    • Coulomb: SI unit of electric charge, equal to the quantity of electricity conveyed in one second by a current of one ampere. One coulomb is approximately 6.25 x 10^18 electrons.
    • Ampere (I): Represents the rate of flow of one coulomb (6.25 x 10^18 electrons) per second through a given cross section.
    • Ampacity: Current carrying capacity of a wire or cable expressed in Amperes.

    Unit of Electric Potential

    • Volt (V): Electrical unit of voltage or potential difference between two points in an electric field.

    Unit of Electric Power

    • Watt (W): Electric power; rate of doing electrical work.

    Unit of Energy

    • Watt-hours (Whr): Energy; capacity for doing work.

    Unit of Resistance

    • Ohm: Resistance that allows one ampere of current to flow when one volt is impressed upon it.
      • DC Circuit: ohm is called resistance (R).
      • AC Circuit: ohm is called impedance (Z).

    Ohm's Law

    • Relationship between Current, Voltage and Resistance:
      • Current in a DC circuit is directly proportional to the voltage and inversely proportional to the resistance of the circuit.
    • Terms and Formula:
      • I = Current (Amperes), V = Voltage (Volts), R = Resistance (Ohms), W = Electric Power (Watts)
      • Formulas: I = V/R, V = IR, R = V/I
    • Other equations: W = I^2R or VI, Whr = I^2R t

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    Description

    Test your knowledge on the differences between Direct Current (DC) and Alternating Current (AC). This quiz covers key characteristics, applications, and advantages of both types of electrical current. Perfect for students or anyone interested in electricity basics.

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