What is the difference between magnetic field and magnetic field lines?

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Jasmine Grover

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Magnetic fields and magnetic field lines are related to each other and are used to describe the behaviour and properties of magnetic fields. The main differences between magnetic fields and magnetic field lines are as follows – 

Magnetic Field Magnetic Field Lines
Magnetic field is a vector quantity that describes the strength and direction of the magnetic force on a charged particle or a magnetic material. Magnetic field lines are a visual representation of the direction and strength of the magnetic field in a given region of space.
Magnetic field is measured in Tesla (T) or Gauss (G). Magnetic field lines have no units.
Magnetic field is continuous and exists throughout a region of space where a magnetic field is present. Magnetic field lines are discrete and do not exist outside the region where a magnetic field is present.
Magnetic field lines point in the direction of the magnetic field at any given point in space. Magnetic field lines are a closed loop that begins and ends on magnetic poles.
The strength of the magnetic field can be calculated at any point in space by measuring the magnetic field vector. The density of magnetic field lines indicates the strength of the magnetic field, with closer lines indicating a stronger field.
The magnetic field is used to calculate the magnetic force on a charged particle or a magnetic material. Magnetic field lines are used to visualize and represent the direction and strength of the magnetic field in a given region of space.

In summary, the magnetic field is a mathematical vector that describes the strength and direction of the magnetic force, while magnetic field lines are a visual representation of the magnetic field that provides information on the direction and strength of the magnetic field at different points in space.

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CBSE CLASS XII Related Questions

  • 1.
    The magnetic field in a plane electromagnetic wave travelling in glass (\( n = 1.5 \)) is given by \[ B_y = (2 \times 10^{-7} \text{ T}) \sin(\alpha x + 1.5 \times 10^{11} t) \] where \( x \) is in metres and \( t \) is in seconds. The value of \( \alpha \) is:

      • \( 0.5 \times 10^3 \, \text{m}^{-1} \)
      • \( 6.0 \times 10^2 \, \text{m}^{-1} \)
      • \( 7.5 \times 10^2 \, \text{m}^{-1} \)
      • \( 1.5 \times 10^3 \, \text{m}^{-1} \)

    • 2.
      Consider a cylindrical conductor of length \( l \) and area of cross-section \( A \). Current \( I \) is maintained in the conductor and electrons drift with velocity \( \vec{v}_d \, (|\vec{v}_d| = \frac{eE}{m} \tau) \), where symbols have their usual meanings. Show that the conductivity of the material of the conductor is given by \[ \sigma = \frac{n e^2 \tau}{m}. \]


        • 3.
          Assertion : Induced emf produced in a coil will be more when the magnetic flux linked with the coil is more. Reason (R): Induced emf produced is directly proportional to the magnetic flux.

            • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
            • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
            • Assertion (A) is true, but Reason (R) is false.
            • Both Assertion (A) and Reason (R) are false.

          • 4.
            Assertion : Photoelectric effect is a spontaneous phenomenon. Reason (R): According to the wave picture of radiation, an electron would take hours/days to absorb sufficient energy to overcome the work function and come out from a metal surface.

              • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
              • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
              • Assertion (A) is true, but Reason (R) is false.
              • Both Assertion (A) and Reason (R) are false.

            • 5.
              Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

                • attract with a force \( \frac{F}{2} \)
                • repel with a force \( \frac{F}{2} \)
                • repel with a force \( F \)
                • attract with a force \( F \)

              • 6.
                In a Young's double-slit experiment, two waves each of intensity I superpose each other and produce an interference pattern. Prove that the resultant intensities at maxima and minima are 4I and zero respectively.

                  CBSE CLASS XII Previous Year Papers

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