Faraday's Law of Electromagnetic Induction
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Questions and Answers

What does Faraday's law of electromagnetic induction state about the induced emf in a circuit?

  • It is equal to the total magnetic field in the circuit.
  • It is equal to the time rate of change of magnetic flux through the circuit. (correct)
  • It is directly proportional to the applied voltage.
  • It depends solely on the resistance of the circuit.

    • What does the negative sign in the formula for induced emf represent?

  • It implies that magnetic flux cannot change.
  • It signifies that no current will flow through the circuit.
  • It shows the direction of the induced current in the circuit. (correct)
  • It indicates that the emf can only be positive.

    • In a coil with N turns, how does the change of flux behave?

  • The change of flux is the same for each turn. (correct)
  • Each turn experiences a different change of flux.
  • There is no change of flux associated with the coil.
  • The change of flux can be ignored for practical purposes.

    • What can happen to sensitive electrical instruments when an electromagnet is activated or deactivated?

    <p>They may be damaged due to induced emfs.</p> Signup and view all the answers

    How is the induced emf mathematically represented according to Faraday's law?

    <p>$ε = - rac{dΦB}{dt}$</p> Signup and view all the answers

    What is one method to obtain a large deflection in an electromagnetic setup?

    <p>Connect the coil to a powerful battery</p> Signup and view all the answers

    What is the purpose of moving the arrangement rapidly towards the test coil?

    <p>To create relative motion and induce electromotive force</p> Signup and view all the answers

    In the example provided, how long does it take for the magnetic field to decrease to zero?

    <p>0.70 s</p> Signup and view all the answers

    What is the resistance of the square loop mentioned in the example?

    <p>0.5 Ω</p> Signup and view all the answers

    What shape is the loop discussed in the example scenario?

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

    What does the angle θ represent in relation to the loop and magnetic field?

    <p>The angle made by the area vector of the coil with the magnetic field</p> Signup and view all the answers

    What device is suggested as a substitute for a galvanometer in the experimental setup?

    <p>A small bulb, like in a torch light</p> Signup and view all the answers

    What does the magnetic flux equation Φ = BA cos θ represent in the example?

    <p>The relationship between magnetic field strength and area</p> Signup and view all the answers

    What is the formula for the power required to push the arm PQ at a constant speed?

    <p>P = Fv</p> Signup and view all the answers

    When mechanical energy is used to move arm PQ, where is this energy dissipated?

    <p>As Joule heat</p> Signup and view all the answers

    According to Faraday’s law, what determines the magnitude of the induced emf?

    <p>The change in magnetic flux over time</p> Signup and view all the answers

    What expression relates charge flow and induced emf as described in the content?

    <p>ΔQ = Ir Δt</p> Signup and view all the answers

    What happens to the magnetic flux when the arm PQ is pulled outward from x = 0 to x = 2b?

    <p>It increases.</p> Signup and view all the answers

    Which of the following statements about the induced emf is correct?

    <p>Induced emf is proportional to the change in magnetic flux.</p> Signup and view all the answers

    What is the effect of resistance r on the power dissipated as Joule heat?

    <p>Power dissipation increases with higher resistance.</p> Signup and view all the answers

    What equation relates induced emf (ε) to the current (I) and resistance (r)?

    <p>ε = Ir</p> Signup and view all the answers

    What is the resulting current in the circuit if the induced emf is 1.0 mV and the resistance is 0.5 Ω?

    <p>2.0 mA</p> Signup and view all the answers

    What is the value of the induced emf when a circular coil with 500 turns is rotated through 180° in 0.25 s in a magnetic field of 3.0 × 10–5 T?

    <p>3.8 mV</p> Signup and view all the answers

    What role does the Earth's steady magnetic field play in the induction of emf according to the content provided?

    <p>It does not induce any emf.</p> Signup and view all the answers

    According to Lenz’s Law, the induced current produced by an emf tends to:

    <p>Resist the change in magnetic flux.</p> Signup and view all the answers

    If a coil has a resistance of 2 Ω, what will be the current if the induced emf is calculated to be 1.9 mA?

    <p>3.8 mA</p> Signup and view all the answers

    How is the initial flux through a coil calculated when it is perpendicular to a magnetic field?

    <p>Using the formula $\Phi_B = BA \cos 0°$.</p> Signup and view all the answers

    What happens to the induced emf when the magnetic flux through a coil changes?

    <p>It varies depending on the rate of change of flux.</p> Signup and view all the answers

    In the provided example, what does the negative sign in the equation for emf indicate?

    <p>The direction of current flow.</p> Signup and view all the answers

    What is observed when the tapping key K is pressed in Experiment 6.3?

    <p>Momentary deflection in the galvanometer</p> Signup and view all the answers

    What happens to the pointer in the galvanometer if the key K is held pressed continuously?

    <p>The pointer does not move</p> Signup and view all the answers

    What is indicated by the galvanometer upon releasing the key K?

    <p>A momentary deflection in the opposite direction</p> Signup and view all the answers

    What does Experiment 6.3 demonstrate about relative motion?

    <p>It can occur between static coils</p> Signup and view all the answers

    What type of circuit is Coil C2 connected to in the experiment?

    <p>A battery through a tapping key</p> Signup and view all the answers

    Which variable influences the momentary deflection in the galvanometer?

    <p>The action of pressing or releasing the tapping key</p> Signup and view all the answers

    Which observation supports the principle of electromagnetic induction in stationary coils?

    <p>Deflection occurs only when current is switched on or off</p> Signup and view all the answers

    What can be inferred about the relationship between the coils in Experiment 6.3?

    <p>They can induce a current without any movement</p> Signup and view all the answers

    Study Notes

    Faraday’s Law of Electromagnetic Induction

    • Relative motion between a magnet and a coil is not necessary for inducing electromotive force (emf).
    • Faraday demonstrated that a stationary coil (C1) can exhibit induced emf when connected to a galvanometer, while a second stationary coil (C2) is powered by a battery.
    • When the circuit key (K) is pressed, a momentary deflection is observed in the galvanometer, indicating induced current.
    • Holding the key causes the galvanometer to return to zero, and releasing it creates deflection in the opposite direction.

    Faraday's Law Equation

    • The induced emf (ε) is proportional to the rate of change of magnetic flux (ΦB) through a circuit:
      • ( ε = - \frac{dΦB}{dt} )
    • The negative sign indicates that the induced current opposes the change in magnetic flux.

    Enhancing Induced emf

    • To achieve a larger deflection in experiments:
      • Insert a soft iron rod inside coil C2.
      • Use a more powerful battery.
      • Increase the speed of relative motion between coils.
    • Replacing the galvanometer with a small bulb can demonstrate induced current visually.

    Example Studies

    • Example 6.2: A square loop with resistance in a magnetic field experiences induced emf when the magnetic field decreases over time:
      • Initial magnetic flux can be calculated using the angle and magnitude of the magnetic field.
      • Results in an induced emf of 1.0 mV and current of 2 mA.
    • The Earth's magnetic field does not induce emf due to its steadiness.

    Lenz’s Law

    • Proposed by Heinrich Friedrich Lenz, which states:
      • The induced emf will create a current opposing the change in magnetic flux that produced it.
    • The negative sign in Faraday's equation reflects this opposition.

    Energy Conversion

    • Mechanical energy used to move a conductor in a magnetic field is transformed into electrical energy and then thermal energy, dissipated as Joule heat.
    • The relationship between charge flow (ΔQ), induced emf, and magnetic flux is established through Faraday's law.

    Additional Example

    • Example 6.8: While moving a rectangular conductor arm in and out of a uniform magnetic field:
      • Expressions for magnetic flux, induced emf, required force, and power dissipation as Joule heat can be derived based on the arm's distance moved and resistance characteristics.

    Key Concepts

    • Electromagnetic induction is a crucial principle in electricity generation and motor operation.
    • Observing the behavior of emf and current in circuits offers insights into electromagnetic properties and energy conversion processes.

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    Related Documents

    Electromagnetic Induction PDF

    Description

    Test your understanding of Faraday's Law of Electromagnetic Induction through this quiz. Explore concepts such as induced emf, the relationship with magnetic flux, and methods for enhancing induced current. Perfect for students studying physics.

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