Science often surprises us with its intriguing concepts. One such fascinating concept in physics is the electric dipole, a setup involving separated positive and negative charges. These opposite charges have equal magnitudes and are separated by a small distance, forming what is known as an electric dipole.



Electric Dipole:

An electric dipole consists of a pair of opposite charges (positive and negative) separated by a small distance. This setup allows for various interesting behaviors, especially when placed in an external electric field.

Behavior of a Dipole in an External Electric Field

When an electric dipole is introduced to a uniform external electric field, it experiences a force. Specifically, the positive charge feels a force in the direction of the field, while the negative charge experiences a force in the opposite direction. Although the net force on the dipole is zero (resulting in translational equilibrium), the dipole undergoes a rotational effect due to these forces.

This rotational effect is known as torque, which causes the dipole to rotate with a certain angular velocity. The torque (τ) experienced by the dipole can be calculated using the formula:

τ = pEsinθ

where:

p is the dipole moment (product of charge and the distance between charges),

E is the magnitude of the external electric field,

θ is the angle between the dipole moment and the electric field.

Read Also: Experiments of Faraday and Henry: Class 12 Physics Notes

Torque and its Calculation

To understand the torque on a dipole, consider the forces acting on the charges. The force on each charge is qE , with opposite directions for the positive and negative charges. This creates a couple, leading to rotational motion.

The magnitude of the torque is given by:

τ= 2qaEsinθ

Here, 2a is the distance between the charges. By defining the dipole moment p=2qa, the formula simplifies to:

τ=pEsinθ

In vector form, torque is represented as the cross product of the electric field and the dipole moment:

τ=p×E

Real-life Example of Dipole and Electric Field

Consider combing your dry hair and then bringing the comb close to small pieces of paper. The comb attracts the paper pieces because it acquires a charge through induction. This charged comb polarizes the paper, creating a dipole moment. The non-uniform electric field generated by the comb causes the paper pieces to move towards it.

Conclusion:

The study of an electric dipole in a uniform external electric field reveals fascinating aspects of electrostatics. The concept of torque acting on a dipole highlights the intricate interplay between electric charges and fields. This rotational effect, governed by the relationship between the dipole moment and the external field, illustrates how forces at a microscopic level translate to observable phenomena. By delving into the principles of torque and dipole moments, we gain deeper insights into the behavior of electric charges, further enriching our comprehension of fundamental physics. This knowledge not only explains everyday occurrences, such as the attraction of paper to a charged comb, but also lays the groundwork for advanced applications in technology and science.