Electromagnetic Induction Flashcards
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Questions and Answers

What is electromagnetic induction?

Electromagnetic induction is the process whereby a conductor and a magnetic field are moved relative to each other to induce (generate) a current or electromotive force (emf).

What does the size of the induced current or emf depend on in a straight wire? (Select all that apply)

  • Speed of movement of the wire (correct)
  • Magnitude of magnetic flux density (correct)
  • Temperature of the wire
  • Length of wire in field (correct)

    • What does the size of the induced current or emf depend on in a solenoid? (Select all that apply)

  • Magnitude of magnetic flux density (correct)
  • Conductivity of the wire
  • Number of turns of the wire (correct)
  • Cross-sectional area of the coil (correct)

    • What happens as a wire moves into a magnetic field and when it moves out of it?

    <p>As a wire moves into a magnetic field, it cuts across the field. When it is removed, it cuts again across the field lines but in the opposite direction.</p> Signup and view all the answers

    What does the cutting of magnetic field lines by a conductor give rise to?

    <p>An induced current in the conductor.</p> Signup and view all the answers

    How is a current or emf induced in a solenoid of N turns?

    <p>If the number of field lines linking it changes, a current or emf is induced.</p> Signup and view all the answers

    When do we use Fleming's right-hand dynamo rule?

    <p>When we provide an external force on a conductor by moving it through a magnetic field, inducing a current.</p> Signup and view all the answers

    Describe what each of the fingers represent in Fleming's right-hand dynamo rule.

    <p>Thumb: F; First finger: B; Middle finger: I (conventional).</p> Signup and view all the answers

    If we've got I and B, which of Fleming's rules do we use to figure out F?

    <p>Left hand motor rule.</p> Signup and view all the answers

    If we've got F and B, which of Fleming's rules do we use to figure out I?

    <p>Right hand dynamo rule.</p> Signup and view all the answers

    How is emf produced in a conductor moving through a magnetic field that is not part of a complete circuit?

    <p>Negative charge accumulates at one end of the conductor, leaving the other end positively charged.</p> Signup and view all the answers

    Why is it emf that is induced and not voltage?

    <p>By pushing the wire through the magnetic field, work is done, and this is transformed into electrical energy - so it is emf, not voltage.</p> Signup and view all the answers

    What is moving the conductor equivalent to in terms of electrons in the conductor?

    <p>Moving the conductor is equivalent to giving an electron within the conductor a velocity in the direction of this motion.</p> Signup and view all the answers

    What is magnetic flux?

    <p>Magnetic flux is the total number of magnetic field lines passing through an area A.</p> Signup and view all the answers

    What is magnetic flux where B is the component of magnetic flux perpendicular to the area?

    <p>φ = BA</p> Signup and view all the answers

    What is magnetic flux when B is not perpendicular to the area?

    <p>φ = BAcosθ</p> Signup and view all the answers

    What is magnetic flux linkage for a coil of N turns?

    <p>Nφ or BANcosθ.</p> Signup and view all the answers

    What are magnetic flux and magnetic flux linkage measured in?

    <p>Weber (Wb).</p> Signup and view all the answers

    What is 1 Wb equal to?

    <p>One Tesla metre-squared. 1 Wb = 1 Tm^2.</p> Signup and view all the answers

    In what three ways is emf induced when a change in magnetic flux linking the circuit occurs? (Select all that apply)

    <p>Changing B</p> Signup and view all the answers

    What is Faraday's law of electromagnetic induction and its equation?

    <p>The magnitude of the induced emf is equal to the rate of change of magnetic flux linkage: E (induced emf) = -Δ(Nφ)/Δt.</p> Signup and view all the answers

    1. What is Lv equal to? 2) What is BLv equal to? 3) What does this therefore mean?

    <p>Lv = rate of change of area.</p> Signup and view all the answers

    A straight wire XY is pushed down a horizontal magnetic field B. Explain the origin of electromagnetic induction.

    <p>Free electrons in the wire are moving downwards too; they are, in effect, an electric current. The motor effect comes into play, and each electron experiences a Bev force, moving left, so the conventional current is right.</p> Signup and view all the answers

    What is electromagnetic induction a consequence of?

    <p>The motor effect.</p> Signup and view all the answers

    What is the charge on the end of a wire where electrons accumulate?

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

    Study Notes

    Electromagnetic Induction

    • Electromagnetic induction involves the generation of current or electromotive force (emf) when a conductor and a magnetic field move relative to each other.

    Induced Current/Emf in a Straight Wire

    • Depends on:
      • Magnitude of magnetic flux density
      • Length of the wire within the magnetic field
      • Speed of movement of the wire

    Induced Current/Emf in a Solenoid

    • Depends on:
      • Magnitude of magnetic flux density
      • Cross-sectional area of the coil
      • Number of wire turns in the coil
      • Rate at which the coil rotates within the magnetic field

    Wire Movement in Magnetic Fields

    • When a wire moves into a magnetic field, it cuts across field lines, inducing current.
    • As it exits the field, it cuts in the opposite direction, also inducing current.

    Cutting Magnetic Field Lines

    • The act of a conductor cutting through magnetic field lines results in an induced current.

    Induced Current in Solenoid

    • In a solenoid with N turns, induced current results from changes in the number of magnetic field lines linking the coil.

    Fleming's Right-Hand Dynamo Rule

    • Applied when a conductor is moved through a magnetic field to induce current.
    • Thumb represents force (F), first finger represents magnetic field (B), middle finger represents current (I).

    Fleming's Left-Hand Rule

    • Used to determine force (F) when current (I) and magnetic field (B) are known.

    Induced Emf in Incomplete Circuits

    • When a conductor moves through a magnetic field without forming a complete circuit, a negative charge accumulates at one end, causing an induced emf.

    Induced Quantity: Emf vs. Voltage

    • Emf is produced due to work done in moving through the magnetic field, converting it to electrical energy, making it distinct from voltage.

    Electron Movement in Conductors

    • Moving a conductor imparts velocity to electrons, equivalent to inducing current.

    Magnetic Flux

    • Defined as the total number of magnetic field lines passing through an area A.

    Magnetic Flux Calculation

    • For B perpendicular to area: φ = BA
    • For B at an angle: φ = BAcosθ

    Magnetic Flux Linkage

    • For a coil with N turns, magnetic flux linkage is expressed as Nφ or BANcosθ.

    Measurement Units

    • Both magnetic flux and magnetic flux linkage are measured in Weber (Wb).
    • 1 Weber is equivalent to one Tesla metre-squared (1Wb = 1Tm²).

    Induced Emf and Changes in Magnetic Flux

    • Emf can be induced through:
      • Changing magnetic field strength (B)
      • Altering the area of the circuit
      • Changing the angle (θ)

    Faraday's Law of Electromagnetic Induction

    • States that the magnitude of induced emf equals the rate of change of magnetic flux linkage: E = -Δ(Nφ)/Δt.

    Relationship Between Variables

    • Lv represents the rate of change of area.
    • BLv represents the rate of change of area concerning magnetic flux density.
    • Consequently, E = BLv holds true.

    Origin of Electromagnetic Induction

    • In the case of a wire pushed in a magnetic field, free electrons experience a downward movement and are influenced by the Bev force, thus generating electric current.

    Consequence of Electromagnetic Induction

    • The phenomenon is fundamentally connected to the motor effect, whereby a magnetic field influences the motion of charged particles.

    Charge Distribution in Wires

    • The end of a wire where electrons accumulate becomes negatively charged.

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    Description

    Test your knowledge on electromagnetic induction with these flashcards. Each card explores key concepts, definitions, and factors affecting induced current or electromotive force. Brush up on your physics fundamentals and understand the relationship between conductors and magnetic fields.

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