In physics, there are two main types of dipoles, a magnetic dipole and an electric dipole. Conceptually, they are similar in that the term dipole means “having two poles". A dipole field is the sum of the electric fields resulting from the dipole at every point in an area, regardless of whether it is an electric dipole or magnetic dipole. The Earth’s magnetic field can be represented by a dipole field.
Electric dipoles are any set of equal and opposite charges, one side positive and one side negative. A hydrogen atom is a dipole as it has one positively charged proton and one negatively charged electron. However, a water molecule is also a dipole because electrons are more attracted to the oxygen atom than the two stable hydrogen atoms.
The dipole field surrounding an electric dipole is the total electric field made up of the electric force due to the two charges within the dipole acting on a positive test charge at every point in the area. This electric field consists of the force on that positive test charge divided by the magnitude of the charge, and it is in the direction of the force. This can be easily seen by drawing arrows to represent the magnitude of the electromagnetic force at every point and then drawing field lines parallel to the direction of the force from one charge to the other. The magnitude and direction of the sum of these forces is the dipole field.
A magnetic dipole is essentially a bar magnet and has two different poles, north and south. The dipole field according to a magnetic dipole is the total magnetic field made up of the magnetic forces at every point in the area. All magnets are dipoles in nature. One of the four electromagnetic equations developed by James Maxwell states that there is no such thing as a magnetic monopole.
In geophysics, Earth’s magnetic field can be represented as a dipole field with magnetic field lines extending from the geographic South Pole to the geographic North Pole. The strength of the dipole field is at a maximum when the field lines are closer together, as in at the North and South poles, and weakens as the field lines get farther apart. A line drawn through the middle of the dipole field, at the Earth’s equator, represents the equatorial plane and is perpendicular to the magnetic field lines.
