Two Dipoles Walked Into A Bar

Electricity and Magnetism Level 1

An electric dipole is a set of two point charges separated by a small distance, that are of the same magnitude but opposite signs. We have two dipoles, arranged as shown above. What force do the two dipoles experience?

Details and Assumptions:

Like charges repel, unlike charges attract.
The force between two charges becomes weaker as the distance between them increases.

They attract They repel They neither attract nor repel

1 solution

Rohit Gupta
Feb 20, 2017

Consider the dipole above. This creates an electric field as shown. The field is towards the right because the point $P$ is closer to the positive charge which creates a field away from it. It should also be noted that this field $E$ decreases as the distance from the dipole increases. Now, another dipole is placed as below.

The first dipole will create a field $E_1$ and $E_2$ at the location of the positive and negative charges of the second dipole, respectively. The field $E_1$ is stronger than the $E_2$ . Therefore, the positive charge of the second dipole will experience a greater force than the negative charge, $F_1 > F_2$ . Hence, the net force will be towards the right or they will $\boxed{\text{repel each other}}$ .

For people that don't know that you're speaking of two magnets with the positive poles facing each other, and can't react to each other as they get closer to each other, this could be confusing.

Jim Hall - 4 years ago

Two Dipoles Walked Into A Bar

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