Electromagnetic Induction Quiz
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Questions and Answers

What is the function of the commutator in a DC generator?

  • To provide a path for the current to flow.
  • To regulate the speed of the generator.
  • To increase the voltage of the output current.
  • To convert AC to DC. (correct)

    • How does a microphone convert sound waves into an electrical signal?

  • By changing the resistance of a material in response to sound pressure variations.
  • By using a piezoelectric crystal that vibrates in response to sound pressure variations.
  • By using an optical sensor that detects changes in light intensity caused by sound waves.
  • By using a fixed magnet and a coil that moves in response to sound pressure variations. (correct)

    • What is the primary function of a transformer?

  • To convert AC to DC.
  • To regulate the flow of current.
  • To amplify the power of electrical signals.
  • To increase the voltage of AC signals. (correct)

    • What would happen if a DC current were applied to the primary coil of a transformer?

    <p>The transformer would not produce any current in the secondary coil. (D)</p> Signup and view all the answers

    Why does a step-up transformer increase the voltage of the secondary coil?

    <p>The secondary coil has more turns of wire than the primary coil. (C)</p> Signup and view all the answers

    What is the effect on the induced current if the speed at which a coil rotates in a magnetic field is increased?

    <p>The induced current increases. (D)</p> Signup and view all the answers

    Which of the following is NOT a factor affecting the size of the current induced in a generator?

    <p>The resistance of the circuit connected to the generator. (A)</p> Signup and view all the answers

    A coil of wire is moved through a magnetic field. What happens to the induced current if the coil is moved faster through the field?

    <p>The induced current increases. (B)</p> Signup and view all the answers

    What is the purpose of the turbine in a power station?

    <p>To convert thermal energy into mechanical energy. (A)</p> Signup and view all the answers

    How does the magnetic field produced by the induced current in a wire moving in a magnetic field interact with the original magnetic field?

    <p>It opposes the original magnetic field. (B)</p> Signup and view all the answers

    Which of the following is true about the current produced by a generator?

    <p>It is always AC current. (B)</p> Signup and view all the answers

    A wire loop is placed in a magnetic field. What happens to the loop if the magnetic field strength is increased?

    <p>A current will be induced in the loop. (A)</p> Signup and view all the answers

    In a simple generator, how is the current induced in the coil?

    <p>By moving the coil within a stationary magnetic field. (B)</p> Signup and view all the answers

    If the power of a transformer is 100%, what is the relationship between the power in the primary circuit and the power in the secondary circuit?

    <p>The power in the primary circuit is equal to the power in the secondary circuit. (D)</p> Signup and view all the answers

    Why are high voltages used to transmit electrical energy over long distances?

    <p>High voltages reduce the current flowing through the transmission wires, minimizing energy loss due to heating. (A)</p> Signup and view all the answers

    What is the purpose of a step-down transformer in the domestic power supply?

    <p>To reduce the voltage to a safe level for household appliances. (C)</p> Signup and view all the answers

    What is the relationship between the number of coils on the primary and secondary sides of a transformer and the voltage ratio?

    <p>The voltage ratio is directly proportional to the ratio of the number of coils on the primary side to the number of coils on the secondary side. (B)</p> Signup and view all the answers

    Why is it essential to reduce the voltage of electricity before it reaches our homes?

    <p>To make it safer to use in homes. (C)</p> Signup and view all the answers

    If the number of coils on the primary side of a transformer is 100 and the number of coils on the secondary side is 20, what is the voltage ratio (Vp/Vs)?

    <p>5 (A)</p> Signup and view all the answers

    Which of the following statements is TRUE about the relationship between voltage and current in a transformer with 100% efficiency?

    <p>As voltage increases, current decreases proportionally. (A)</p> Signup and view all the answers

    What is the primary function of a step-up transformer in the national grid?

    <p>To increase the voltage for safer transmission over long distances. (A)</p> Signup and view all the answers

    Flashcards

    Current Induction

    Current is induced when a wire moves through a magnetic field.

    Potential Difference

    A difference in electric potential that causes electrons to move in a conductor.

    Induced Current

    Current flows if the conductor is part of a circuit during induction.

    Opposition of Fields

    The induced magnetic field opposes the change in the original magnetic field.

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    Small-scale Generation

    Spinning a coil in a magnetic field generates small currents measured by an ammeter.

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    Large-scale Generation

    Turbines in power stations generate electricity by spinning coils in a magnetic field.

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    Factors affecting Current/Voltage

    Current/Voltage size depends on loops, rotation speed, and magnetic strength.

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    Alternator vs. Dynamo

    Alternators produce AC by reversing current; dynamos work similarly but produce different outputs.

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    Commutator

    A metal ring that reverses the current's sign in a coil.

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    Direct Current (DC)

    Electricity that flows in one direction, produced by the commutator.

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    Microphone function

    Uses a coil moving in a magnetic field to produce a current proportional to sound.

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    Transformer function

    Device that transfers energy between coils, inducing AC current in secondary coil.

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    Step-up transformer

    Has more coils in the secondary, increasing voltage from the primary.

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    Step-down transformer

    A device that reduces voltage from primary to secondary side.

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    Transformer equation

    Np/Ns = Vp/Vs; relates coil counts and voltages in transformers.

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    National Grid

    System for transferring electrical energy at high voltages.

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    High voltage advantage

    High voltages reduce current, minimizing energy loss.

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    Power relationship in transformers

    Power in primary equals power in secondary if 100% efficient (P_primary = P_secondary).

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    Voltage and current relationship

    As voltage increases, current decreases for constant power.

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    Efficiency in energy transmission

    Reducing current by increasing voltage minimizes energy loss during transmission.

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    Study Notes

    Electromagnetic Induction

    • Current Induction: A current is induced if a wire moves in a magnetic field. The conductor creates a potential difference, and if connected in a circuit, a current flows. The induced current's magnetic field opposes the original change.

    • Production (Small-Scale): Spinning a wire coil in a magnetic field creates a small current, detectable with a sensitive ammeter. Passing a wire through a magnetic field also induces a current.

    • Production (Large-Scale): Power stations use steam turbines, driven by combustion or nuclear fission, which turn coils of wire in a magnetic field to generate large currents (generators).

    Factors Affecting Induced Current

    • Number of Coils: More coils produce a larger current.
    • Speed of Rotation: Faster rotation means a larger current.
    • Magnetic Field Strength: A stronger magnetic field produces a larger current.

    Alternators

    • Alternating Current (AC): The current switches direction every half-turn. A commutator is not needed.
    • Mechanism: The coil rotates in a magnetic field. The direction of the induced current reverses with each half-turn.

    Dynamos

    • Direct Current (DC): The current flows in one direction. A commutator reverses the current every half-turn.
    • Mechanism: Same setup as an alternator, but a commutator ensures a continuous flow in one direction.

    Microphones and Loudspeakers

    • Mechanism: Sound waves cause a coil to vibrate within a magnetic field, inducing a proportional current. This current can drive a loudspeaker, which produces sound through its cone movements.

    Transformers

    • Alternating Current (AC) Necessity: Transformers only work with alternating current (AC) to produce a changing magnetic field.
    • Step-Up Transformers: Increase voltage by having more coils on the secondary coil than primary.
    • Step-Down Transformers: Decrease voltage by having fewer coils on the secondary coil than primary.
    • Relationship: Voltage ratio is proportional to the number of coils ratio. The power in the primary is equal to the power in the secondary.
    • National Grid: High voltages are used to transfer energy between power stations efficiently over long distances across the national grid.

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    Related Documents

    Edexcel GCSE Physics: Electromagnetic Induction Notes PDF

    Description

    Test your knowledge on electromagnetic induction concepts, including current induction, production methods, and factors affecting induced current. This quiz covers both small and large-scale applications, as well as details about alternators and alternating current.

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