An electric dipole is placed in a uniform electric field. What will be the net electric force on the dipole?

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Ques: An electric dipole is placed in a uniform electric field. What will be the net electric force on the dipole?

Ans: The net force on electric dipole when it is placed in a uniform electric field is “zero”. 

Explanation: When an electric dipole is placed in a uniform electric field, the electric field exerts a force on each charge of the dipole. Since the charges in a dipole are of equal magnitude but opposite in sign, the force acting on them also becomes equal in magnitude but opposite in direction.

electric dipole placed in a uniform electric field

Electric dipole placed in a uniform electric field

The force on the positive charge of the dipole is in the direction of the electric field, and the force on the negative charge is in the opposite direction.

  • As a result, the two forces create a torque on the dipole, which tends to rotate it.
  • The force on +q is directed to the right and on −q is to the left.
  • The magnitude of forces are equal as the electric field is uniform. Hence, the net force is always zero.

However, the net electric force on the dipole is always zero because the electric field is uniform and the two forces on the charges are equal and opposite in direction. This means that the electric force on the dipole's center of mass is zero, and the dipole will not experience any translational acceleration in the electric field.

Therefore, the electric dipole experiences only a torque in a uniform electric field, but the net force is always zero.

CBSE CLASS XII Related Questions

  • 1.

    (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.


      • 2.

        A circular coil of 100 turns and radius $\left(\frac{10}{\sqrt{\pi}}\right)$ cm carrying current of $5.0\,\text{A}$ is suspended vertically in a uniform horizontal magnetic field of $2.0\,\text{T}$. The field makes an angle $30^\circ$ with the normal to the coil. Calculate:

        (I) the magnetic dipole moment of the coil, and

        (II) the magnitude of the counter torque that must be applied to prevent the coil from turning.


          • 3.

            A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of $60^\circ$ in 0.2 s. The value of emf induced in the loop will be:

              • 5 V
              • 3.5 V
              • 2.5 V
              • Zero V

            • 4.
              In a region, the electric potential varies as \(V = 10 - 50x\), where \(V\) is in volts and \(x\) is in meters. The electric field in the region is

                • \(10\ \text{N/C}\) along \(+x\)
                • \(10\ \text{N/C}\) along \(-x\)
                • \(50\ \text{N/C}\) along \(+x\)
                • \(50\ \text{N/C}\) along \(-x\)

              • 5.
                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.


                  • 6.

                    A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is (i) $\sqrt{2}$, and (ii) $\sqrt{3}$.

                      CBSE CLASS XII Previous Year Papers

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