Electromagnetic Induction

• What is the definition of a magnetic field?

  It is the region or space around a magnet or a current carrying conductor where charged particles experience a force.

  
• What is the SI unit of magnetic field?

  Tesla (T)

  
• What do magnetic field lines represent?

  They represent the direction of the magnetic field at any point.
• What are the properties of magnetic field lines?

  • Continuous and closed curves traveling from north to south outside the magnet and south to north inside.
  • Form closed loops unlike electric field lines.
  • The tangent at any point shows the direction of the magnetic field.
  • Do not intersect each other.
  • Widely spaced lines indicate a weak magnetic field; closely spaced lines indicate a strong magnetic field.
  • Parallel and equidistant lines indicate a uniform magnetic field.
• What does it mean if magnetic field lines are widely spaced?

  It represents a weak magnetic field.

  
• What is magnetic flux?

  It is the number of magnetic lines of force passing through a surface held in the magnetic field.
• What is the SI unit of magnetic flux?

  Weber (Wb)
• How is one Weber defined?

  One Weber is the amount of magnetic flux over a surface area of 1 m² lying perpendicular to a magnetic field of 1 Tesla.
• What is flux linkage?

  Flux linkage is given by $N \cdot ∅_B$, where N is the number of turns in the coil.
• What is the C.G.S unit of magnetic flux?

  Maxwell
• What is the relation between SI unit and CGS unit of magnetic flux?

  1 Wb = 10⁸ Maxwell

  
• What factors affect magnetic flux?

  • Magnitude or strength of magnetic field (B)
  • Area (A) of the coil
  • Angle (θ) between the area vector and the direction of the magnetic field

  
• When is magnetic flux positive, zero, or negative?

  Positive for lines of force pointing outwards, zero for no lines, and negative for lines entering the surface.

  
• What is the difference between dot product and cross product of vectors?

  The dot product is a scalar quantity, while the cross product is a vector quantity.
• What is magnetic flux density?

  It is the magnetic flux passing through a unit cross-section.

  
• What is the SI unit of magnetic flux density?

  Wb/m² or Tesla (T)

  
• How does magnetic flux density relate to magnetic field?

  Magnetic flux density is the same as magnetic field.
• What is electromagnetic induction?

  It is the production of emf or current in a conductor due to varying magnetic flux linked with the conductor.
• What is induced emf?


  It is the emf induced in the conductor due to electromagnetic induction.
• What is the significance of Faraday's experiments?

  They demonstrate the change of magnetic flux linked with a conductor induces electric current.

  
• What are the methods to achieve electromagnetic induction according to Faraday's experiments?

  1. Relative motion between magnet and coil.

  2. Relative motion between coils.

  3. Change in current flowing in a neighboring circuit (making and breaking of circuit).

  
• What happens when a magnet is pushed towards a coil in Faraday's first experiment?

  The galvanometer deflects, indicating the presence of electric current in the coil.

  
• What occurs when the magnet is pulled away from the coil in Faraday's first experiment?

  The galvanometer shows deflection in the opposite direction, indicating reversal of the current's direction.

  
• How does the speed of the magnet affect the galvanometer's deflection in Faraday's first experiment?

  The deflection increases if the magnet is moved with greater velocity.

  
• What is the effect of moving coil C2 towards coil C1 in Faraday's second experiment?

  The galvanometer shows a deflection, indicating electric current is induced in coil C1.

  
• What happens when coil C2 is moved away from coil C1 in Faraday's second experiment?

  The galvanometer shows a deflection in the opposite direction.

  
• What is observed when the tapping key is pressed in Faraday's third experiment?

  The galvanometer shows a momentary deflection.
• What happens when the tapping key is held pressed continuously in Faraday's third experiment?

  There is no deflection in the galvanometer.
• What is the significance of the momentary deflection when the key is released in Faraday's third experiment?

  It indicates that change in magnetic flux in the primary coil induces an emf in the secondary coil.

  
• What are Faraday's laws of electromagnetic induction?

  1. The induced emf in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.

  2. The direction of induced emf is such that it opposes the change in magnetic flux that produced it (Lenz's Law).

  
• What are the two coils in the experiment called?

  Primary and secondary coils
• What happens to the galvanometer when the tapping key is pressed?

  It shows a momentary deflection
• What occurs when the tapping key is held pressed continuously?

  There is no deflection in the galvanometer
• What is observed when the tapping key is released?

  A momentary deflection in the opposite direction is observed
• When does the galvanometer show deflection?

  Only when there is a make and break in the primary circuit
• What does the change in magnetic flux in the primary coil induce in the secondary coil?

  An electromotive force (emf)

  
• What is Faraday's first law of electromagnetic induction?

  Whenever there is a change in magnetic flux linked with the coil, an emf is induced

  
• How long does the induced emf last according to Faraday's first law?

  As long as the change of magnetic flux in the coil continues
• What does Faraday's second law state about the magnitude of induced emf?

  The magnitude of induced emf is directly proportional to the rate of change of magnetic flux

  
• What is the mathematical expression for induced emf according to Faraday's second law?

  $e =$$-\frac{d\Phi_B}{dt}$