Paramagnetism is the weak attraction of some materials to an external magnetic field because they have unpaired electrons. In Principles of Physics II, you use it to explain how matter responds to magnetism at the microscopic level.
Paramagnetism in Principles of Physics II is the magnetic response of a material with one or more unpaired electrons. When you place that material in an external magnetic field, some of its tiny magnetic moments line up with the field, so the material is pulled weakly toward the stronger field region.
The reason this happens is microscopic. Electrons act like tiny magnets because they have spin and orbital motion. In a paramagnetic substance, the magnetic moments do not cancel completely, so the material has a net tendency to respond to a field. Without an external field, those moments point in random directions, so the material does not show a strong overall magnetization.
The effect is usually small because thermal motion keeps jostling the atoms and molecules around. At ordinary temperatures, the alignment is only partial, so paramagnets do not grab onto magnets the way iron does. If the field is stronger, the alignment becomes more noticeable, but it is still a weak effect compared with ferromagnetism.
A helpful way to picture it is to compare a paramagnet with a pile of loose compass needles. A magnetic field nudges them to point the same way, but the needles do not lock into a fixed pattern on their own. As soon as the external field is removed, the alignment fades and the material returns to its nonmagnetic state.
Examples often mentioned in Physics II include aluminum, platinum, and ions like iron(III), which have unpaired electrons. These examples show that paramagnetism is not about whether a substance is metal or nonmetal, but about whether its electrons leave any magnetic moments uncanceled. That microscopic detail is what turns a material into a weak magnet in the presence of a field.
Paramagnetism shows you how magnetic fields interact with matter, not just with moving charges or wires. In Principles of Physics II, that matters because the course keeps connecting field behavior to the materials placed inside the field, whether you are looking at lab demonstrations, magnetic properties of substances, or the parts of a device that must respond predictably to magnetism.
It also gives you a clean contrast with the other major magnetic behaviors. If you know why a material is paramagnetic, you can tell it apart from diamagnetic materials, which weakly repel fields, and ferromagnetic materials, which can keep magnetization after the external field is gone. That comparison comes up often because many homework and quiz questions are really asking you to identify which mechanism is happening from a short description or a data trend.
Paramagnetism also connects directly to the idea of magnetic moment. When you see a material with unpaired electrons, you should be thinking about the net microscopic moments and how an external field changes their orientation. That kind of reasoning shows up in conceptual questions, material comparisons, and lab observations where you interpret why one sample reacts more strongly than another.
The temperature dependence matters too. If the temperature rises, thermal agitation makes alignment harder, so the magnetic response gets weaker. That gives you a cause and effect pattern you can use when a problem asks why a sample becomes less responsive under hotter conditions.
Keep studying Principles of Physics II Unit 6
Visual cheatsheet
view galleryDiamagnetism
Diamagnetism is the other weak, field-driven response you compare with paramagnetism. Diamagnetic materials have all their electrons paired, so they create a tiny induced field that opposes the applied field instead of lining up with it. If a question asks why one sample is repelled a little while another is attracted a little, this is usually the comparison to make.
Ferromagnetism
Ferromagnetism is much stronger than paramagnetism because magnetic moments in the material can align into domains and stay aligned. That is why iron can become a permanent magnet, while a paramagnetic sample loses its magnetization when the external field is removed. In Physics II, this contrast helps you separate a temporary response from a lasting one.
Magnetic Moment
A magnetic moment is the tiny vector quantity that tells you how a particle or object responds to a magnetic field. Paramagnetism comes from having unpaired electrons, which means the material has nonzero microscopic magnetic moments. When you explain the mechanism, this is the quantity you are really tracking.
Magnetic Permeability
Magnetic permeability describes how easily a material supports a magnetic field inside it. Paramagnetic materials have a permeability slightly greater than that of free space, which matches their weak attraction to the field. In problem-solving, this shows up when you compare how different materials change the field inside a region.
A quiz or problem-set question on paramagnetism usually asks you to identify the material behavior from a description, explain why a sample is weakly attracted to a magnet, or compare it with diamagnetism and ferromagnetism. You might also see a graph or lab result where the response gets stronger in a stronger field or weaker at higher temperature.
When you answer, point to unpaired electrons and partial alignment of magnetic moments. If the prompt mentions that the effect disappears when the field is removed, that is your clue that the material is not ferromagnetic. In a lab write-up, you may need to explain why a substance like aluminum shows only a small pull toward a magnet instead of sticking to it.
These are easy to mix up because both involve attraction to a magnetic field, but the strength and permanence are very different. Paramagnetism is weak and temporary, with no leftover magnetization after the field is removed. Ferromagnetism is strong, usually involves domains, and can retain magnetization.
Paramagnetism is a weak attraction to an external magnetic field caused by unpaired electrons.
The magnetic moments in a paramagnetic material line up partly with the field, but only while the field is present.
Paramagnetic materials do not stay magnetized after the field is removed.
Higher temperature usually weakens paramagnetism because thermal motion makes alignment harder.
In Physics II, paramagnetism is mainly a comparison point for diamagnetism, ferromagnetism, and magnetic moments.
Paramagnetism is the weak attraction of a material to an external magnetic field because it has unpaired electrons. The field causes some of the material's magnetic moments to line up with the field. Once the field is gone, the alignment disappears.
Paramagnetism is much weaker and does not leave the material magnetized after the field is removed. Ferromagnetism is stronger because magnetic domains can align and stay aligned. If a problem mentions permanent magnetization, you are usually not looking at paramagnetism.
Unpaired electrons give a material a net magnetic moment instead of canceling everything out. That net moment can line up with an external magnetic field, which is what creates the weak attraction. If all electrons are paired, the material is more likely to be diamagnetic instead.
Common examples include aluminum, platinum, and some ions such as iron(III) ions. These substances have unpaired electrons, so they respond weakly to a magnetic field. In class problems, examples are often used to test whether you can connect electron structure to magnetic behavior.