Electric Polarization

Claimed by Jae

The Main Idea

Electric polarization is the process of inducing an object to separate charges inside it. One portion of the object would be mostly positive charges and the other portion would be mostly negative.

When an object is charged, either positively or negatively, it is attracted to another object through polarization. Even if the net charge of the second object is zero, it would still be attracted to the first object. Although the neutral object initially does not make an electric field that attracts or repels the charged object, the charged object affects the neutral object to be an induced dipole. However, this dipole is not permanent. If the charged object is removed, there would be no electric field applied and no polarization. The induced dipole will go back to being a neutral object.

Structure of atom explains polarization. Protons in an atom are in the nucleus, and they are tightly bound. However, electrons located in the electron cloud of an atom are loosely bound compared to the protons. Therefore, the electrons can be induced to move to one side of the atom, and this phenomenon causes polarization of the atom, making it to be an induced dipole.

Polarization for insulators occurs in a different manner from conductors. When a conductor is polarized, electrons move across the surface of one side of the conductor to the other side. Unlike conductors, in insulators, electrons are not able to freely move around. Thus, individual molecules in the insulators are polarized, but electrons move only small distance compared to the case in conductors, so the charges are not on the surface of the object. Excess charges on conductors can only exist on the surface, while they exist anywhere on or inside insulators.

Polarization is a different idea from charging or discharging. While polarization causes a separation of charges in an object, it does not cause imbalance of charges, which forms a charged object. Polarization still maintains an equal number of protons and electrons in an object. Therefore charging is a different discussion from polarization.

Connectedness

Polarization is one of the main ideas in electricity and occurs whenever there is a charged object near another object. Real life applications includes when a balloon sticks to a wall after it is charged. Balloon causes the wall to polarized, and it is attracted to it in the air. As for PHYS 2212, polarization is one of the main topic covered in the course, frequently appearing as test questions. Possible questions include drawing how a conductor or an insulator would be polarized when located near a positively or negatively charged object.