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.
    If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.


      • 2.
        Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

          • 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.

        • 3.
          Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.


            • 4.
              Two heaters rated as \((P_1,V)\) and \((P_2,V)\) are connected in series across a dc source of \(V/2\) volt. The power consumed by the combination will be –

                • \((P_1+P_2)\)
                • \(\dfrac{P_1+P_2}{2}\)
                • \(\dfrac{P_1P_2}{2(P_1+P_2)}\)
                • \(\dfrac{P_1P_2}{4(P_1+P_2)}\)

              • 5.
                Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.


                  • 6.
                    A light copper ring is freely suspended by a light string. A bar magnet is held horizontally with its length along the axis of the ring. The magnet is moved towards the ring with its N pole facing the loop. What will happen to the ring and its position? Explain.

                      CBSE CLASS XII Previous Year Papers

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