Electric Currents: DC vs AC
30 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary difference between direct current (DC) and alternating current (AC)?

  • DC flows in one direction, while AC flows in both directions. (correct)
  • DC can be generated with AC generators.
  • AC has a constant value, while DC changes value.
  • AC has fixed terminals, while DC does not.

    • Which of the following is a source of direct current?

  • Transformers
  • Solar panels
  • AC generators
  • Batteries (correct)

    • How many wires does a single-phase supply typically use?

  • Two wires (correct)
  • Three wires
  • Four wires
  • One wire

    • Which statement correctly describes the function of a cell?

    <p>A cell converts chemical energy into electrical energy.</p> Signup and view all the answers

    Which of the following is true regarding the differences between a cell and a battery?

    <p>A battery consists of multiple cells connected together.</p> Signup and view all the answers

    What type of chemical reaction occurs in primary cells?

    <p>Irreversible reaction that cannot be reused</p> Signup and view all the answers

    Which statement accurately describes a secondary cell?

    <p>It can be recharged and reused.</p> Signup and view all the answers

    What does the longer line in the symbol of an electric cell represent?

    <p>The positive polarity of the cell</p> Signup and view all the answers

    What is a battery comprised of?

    <p>Multiple cells connected together</p> Signup and view all the answers

    In which situation is the neutral (N) wire essential in three-phase supply?

    <p>It is optional in three-phase supply configurations</p> Signup and view all the answers

    What is a characteristic of zinc-carbon batteries?

    <p>They are packaged in a zinc can.</p> Signup and view all the answers

    Which type of battery typically has the longest shelf-life?

    <p>Alkaline battery</p> Signup and view all the answers

    What happens if alkaline batteries are charged?

    <p>They may leak hazardous liquids and explode.</p> Signup and view all the answers

    What is the nominal voltage of Nickel-Cadmium batteries?

    <p>1.2 V</p> Signup and view all the answers

    Which statement is correct regarding the use of zinc-carbon and alkaline batteries?

    <p>Both batteries have the same nominal emf.</p> Signup and view all the answers

    What differentiates the flow of direct current (DC) from that of alternating current (AC)?

    <p>DC has a constant value and flows in one direction, while AC varies and flows in both directions.</p> Signup and view all the answers

    Which of the following statements correctly explains the structural differences between single-phase and three-phase supply?

    <p>Single-phase supply usually involves a phase and a neutral wire, while three-phase supply consists of three or four wires.</p> Signup and view all the answers

    Which device is commonly used as a source of direct current (DC)?

    <p>DC generator</p> Signup and view all the answers

    What is a significant characteristic of the terminal arrangement in direct current (DC) sources?

    <p>DC sources maintain fixed positive and negative terminals.</p> Signup and view all the answers

    What is the main disadvantage of using single-phase power supply compared to three-phase supply?

    <p>Single-phase supply can provide less power over longer distances.</p> Signup and view all the answers

    What is a key characteristic that differentiates alkaline batteries from zinc-carbon batteries?

    <p>Alkaline batteries have an alkaline electrolyte, while zinc-carbon batteries have an acidic one.</p> Signup and view all the answers

    What defines the irreversibility of the chemical reaction in primary cells?

    <p>Chemical energy is never converted back to electrical energy.</p> Signup and view all the answers

    Which battery type is specifically noted for having a risk of leakage and explosion if charged?

    <p>Alkaline battery</p> Signup and view all the answers

    Which of the following statements accurately describes the applications of nickel-cadmium batteries?

    <p>They are rechargeable and used in portable electronics.</p> Signup and view all the answers

    What aspect of secondary cells distinguishes them from primary cells?

    <p>Their reactions can be reversed during charging.</p> Signup and view all the answers

    What is the nominal emf of a zinc-carbon battery?

    <p>1.5 V</p> Signup and view all the answers

    Which statement correctly applies to the construction of batteries?

    <p>Batteries can be made up of either primary or secondary cells.</p> Signup and view all the answers

    Why is the neutral (N) wire optional in a three-phase supply system?

    <p>Its necessity depends on the type of load being driven.</p> Signup and view all the answers

    What is a common usage characteristic of both zinc-carbon and alkaline batteries?

    <p>They both have a nominal voltage of 1.5 V.</p> Signup and view all the answers

    What feature does the longer line in the symbol of an electric cell specifically represent?

    <p>The positive terminal.</p> Signup and view all the answers

    Study Notes

    Electric Power Sources

    • Electric current can be classified as Direct Current (DC) or Alternating Current (AC).
    • DC flows in a single direction with a constant value, while AC changes direction and value periodically.
    • Common sources of DC include batteries and DC generators, which have fixed positive and negative terminals.
    • AC is typically generated by AC generators, available in single-phase and three-phase types.

    Types of Current Supply

    • Single-Phase Supply:
      • Consists of two wires: phase (L) and neutral (N).
    • Three-Phase Supply:
      • Comprises three wires (L1, L2, L3) or four wires (L1, L2, L3, N), with the neutral wire being optional.

    Cells and Batteries

    • A cell is an electrochemical unit converting chemical energy to electrical energy.

    • It comprises two electrodes (anode and cathode) and a low-moisture electrolyte paste.

    • Cells are categorized as:

      • Primary Cells: Non-rechargeable, irreversible chemical reactions.
      • Secondary Cells: Rechargeable, reversible chemical reactions.

    • The symbol for an electric cell features two vertical lines, with the longer representing the positive terminal and the shorter the negative terminal.

    • A battery consists of multiple cells connected together.

    Types of Batteries

    • Zinc-Carbon Battery:

      • Non-rechargeable, typically 1.5 V, inexpensive, used in low-power devices.

    • Alkaline Battery:

      • Mostly non-rechargeable with a nominal 1.5 V, higher energy density than zinc-carbon.

    • Nickel-Cadmium Battery:

      • Rechargeable, 1.2 V, used in portable electronics and power tools.

    • Nickel-Metal Hydride Battery:

      • Rechargeable, 1.2 V, commonly found in consumer electronics.

    • Lithium-Ion Battery:

      • Rechargeable, 3.6 V, used in digital cameras and portable devices.

    • Lead-Acid Battery:

      • Rechargeable, 3.6 V, widely used in vehicles, requires proper disposal due to toxicity.

    Battery Recycling

    • Many batteries, especially those from electronics, can be recycled to conserve natural resources.
    • NiMH batteries are considered eco-friendly, while NiCd batteries contain toxic metals and need careful disposal.

    Renewable Energy Sources

    • The reliance on fossil fuels has raised environmental concerns due to pollution and greenhouse gas emissions.

    • Countries are increasingly investing in renewable energy sources to reduce carbon footprints.

    • Solar Power:

      • Converts sunlight into electricity using photovoltaic (PV) cells, now used in both small and large applications like rooftop panels.

    • Wind Power:

      • Harnesses wind energy via turbines, with significant investments in countries such as the US, Germany, and China.

    • Hydropower:

      • Uses flowing water to generate electricity, prominently found in countries with large rivers like China and India.

    Electric Power Sources

    • Electric circuits utilize two types of current: direct current (DC) and alternating current (AC).
    • DC flows in one direction with a constant value, while AC flows in both directions with a continuously changing value.

    Sources of Direct Current (DC) and Alternating Current (AC)

    • Common sources of DC include:
      • Batteries
      • DC generators
    • Common sources of AC include:
      • AC generators
      • Single-phase and three-phase systems

    Types of AC Supply

    • In Singapore, two common types of AC power supply are:
      • Single-phase supply: uses two wires (phase and neutral).
      • Three-phase supply: can use three wires (L1, L2, L3) or four wires (including neutral).

    Cells

    • A dry cell contains a low-moisture electrolyte that enables chemical reactions to convert chemical energy into electrical energy.
    • Cells are categorized as:
      • Primary cells: non-rechargeable, irreversible chemical reaction.
      • Secondary cells: rechargeable, reversible chemical reaction.
    • The symbol for a cell features two vertical lines, with the longer line representing positive polarity.

    Batteries

    • A battery consists of multiple cells connected together.
    • Common battery types include:
      • Zinc-Carbon Battery: Non-rechargeable, 1.5 V, used in low-power devices.
      • Alkaline Battery: Non-rechargeable, 1.5 V, better energy density and shelf-life than zinc-carbon batteries.
      • Nickel-Cadmium Battery: Rechargeable, 1.2 V, used in low-power portable electronics.
      • Nickel-Metal Hydride Battery: Rechargeable, 1.2 V, used in various consumer electronics.
      • Lithium-Ion Battery: Rechargeable, 3.6 V, widely used in digital devices due to high energy density.
      • Lead-Acid Battery: Rechargeable, 3.6 V, commonly used in motor vehicles, requires proper disposal due to toxicity.

    Recycling Batteries

    • Batteries such as lithium-ion can be recycled to conserve resources.
    • NiMH batteries are eco-friendly, while NiCd and other toxic batteries require careful disposal to avoid environmental harm.

    Renewable Energy Sources

    • There is a global shift towards renewable energy to reduce reliance on fossil fuels, which contribute to greenhouse gas emissions and climate change.
    • Solar Power: Converts sunlight into electricity using photovoltaic cells, which can power small and large devices.
    • Wind Power: Utilizes wind turbines to generate clean electricity, with investment from countries like the USA, Germany, and China.
    • Hydropower: Harnesses water energy, prevalent in countries with large river systems like China and India.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    SET Chapter 6 PDF
    Electric Power Sources PDF

    Description

    This quiz covers the fundamental concepts of direct current (DC) and alternating current (AC). You will learn to distinguish between the two types of current, identify their sources, and understand the functions of cells and batteries. Test your knowledge on symbols and definitions related to electric currents.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser