What is Motional EMF?

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Motional EMF refers to the voltage generated in a conductor that is moving in a magnetic field. When a conductor moves in a magnetic field, the magnetic flux through the conductor changes, and this changing flux induces an electric field within the conductor, causing a voltage to be generated.

The magnitude of the motional EMF is given by the formula:

EMF = Blv

where B is the magnetic field strength, l is the length of the conductor that is moving, and v is the velocity of the conductor.

Motional EMF is the basis of operation for many electrical devices such as electric generators, which convert mechanical energy into electrical energy, and electric motors, which convert electrical energy into mechanical energy. It is also an important concept in the field of electromagnetism and plays a crucial role in understanding the behavior of electric circuits.

One practical example of motional EMF is the operation of a simple generator. In a generator, a coil of wire is rotated inside a magnetic field, generating an EMF in the coil. This EMF can be used to power electrical devices or to charge batteries.

Motional EMF

Motional EMF

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CBSE CLASS XII Related Questions

  • 1.

    Find the ratio $\dfrac{\lambda_\alpha}{\lambda_p}$ of the de Broglie wavelength $\lambda_\alpha$ associated with an alpha particle to the de Broglie wavelength $\lambda_p$ associated with a proton if both are moving with the same velocity.


      • 2.

        A rectangular loop of size 5 cm $\times$ 8 cm is lying in the $x$-$y$ plane in a uniform magnetic field $\vec{B} = (2.0\ \text{T})\hat{k}$. The total magnetic flux linked with the loop is:

          • 80 Wb
          • 16 Wb
          • \(8 \times 10^{-2}\) Wb
          • \(8 \times 10^{-3}\) Wb

        • 3.

          (I) The real image of an object placed between $f$ and $2f$ from a convex lens can be seen on a screen placed at the image location. If the screen is removed, is the image still there? Explain.

          (II) Plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances? Explain.


            • 4.
              A wire of length \(L\) is bent round into (i) a square coil having \(N\) turns and (ii) a circular coil having \(N\) turns. The coil in both cases is free to turn about a vertical axis coinciding with the plane of the coil, in a uniform, horizontal magnetic field and carry the same currents. Find the ratio of the maximum value of the torque acting on the square coil to that on the circular coil.


                • 5.
                  A current of \(4.0\,\text{A}\) flows through a wire of length \(1\,\text{m}\) and cross-sectional area \(1.0\,\text{mm}^2\), when a potential difference of \(2\,\text{V}\) is applied across its ends. Calculate the resistivity of the material of the wire.


                    • 6.

                      A parallel beam of monochromatic light falls normally on a single slit of width $a$ and a diffraction pattern is observed on a screen placed at distance $D$ from the slit. Explain:

                      (I) the formation of maxima and minima in the diffraction pattern, and

                      (II) why the maxima go on becoming weaker and weaker with its increasing number $n$.

                        CBSE CLASS XII Previous Year Papers

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