---
title: "Hysteresis in Principles of Physics II"
description: "Hysteresis is the lag between a changing magnetic field and a material’s response in Principles of Physics II, producing a loop and energy loss."
canonical: "https://fiveable.me/principles-physics-ii/key-terms/hysteresis"
type: "key-term"
subject: "Principles of Physics II"
unit: "Unit 7"
---

# Hysteresis in Principles of Physics II

## Definition

Hysteresis is the lag between an input and a system’s response. In Principles of Physics II, it shows up most clearly in magnetic materials, where magnetization does not retrace the same path as the applied field.

## What It Is

Hysteresis in Principles of Physics II is the lag between what you put into a system and what the system gives back, especially when a magnetic material is driven by a changing magnetic field. If you plot magnetization against the applied field, the path going up is not the same as the path coming back down. That loop is the visual sign that the material does not respond instantly or perfectly reversibly.

The most common physics II example is magnetic hysteresis in ferromagnets. When the external field gets stronger, magnetic domains inside the material line up. When the field is reduced, they do not all snap back to the original random arrangement right away. Some alignment remains, so the material keeps some magnetization even after the field is removed. That leftover magnetization is called remanence or residual magnetism.

To erase that magnetization, you usually have to apply a field in the opposite direction. The value needed to drive the magnetization back to zero is called the coercive field. Materials with a wide hysteresis loop keep magnetization more strongly and lose more energy each cycle. Materials with a narrow loop switch more easily and waste less energy.

The loop matters because the area inside it represents energy lost per cycle. That energy does not disappear from the universe, it is converted mostly into thermal energy inside the material. In real devices, that loss shows up as unwanted heating and reduced efficiency. This is one reason transformer cores and motor components are designed with low-hysteresis materials.

A helpful way to think about hysteresis is to separate cause from response. The field you apply is the cause, but the magnetic state depends on the material’s history, not just the current value of the field. That history dependence is what makes hysteresis different from a simple proportional relationship like Hooke’s law or Ohm’s law.

## Why It Matters

Hysteresis shows you that magnetic materials have memory. In Principles of Physics II, that memory changes how you predict the behavior of cores, switches, motors, and other devices that depend on changing magnetic fields. If you ignore hysteresis, you can predict the wrong magnetization, the wrong field reversal point, or the wrong amount of heating.

It also connects directly to energy loss. When a field cycles repeatedly, the loop area tells you how much energy is being converted into internal energy each cycle. That is a practical idea, not just a graph feature. Engineers care about it because wasted energy means lower efficiency and more heat to manage.

This term also ties into the course’s bigger story about induction. Hysteresis often appears alongside eddy currents, since both can waste energy when magnetic fields change. Even though they are different mechanisms, they show up together in real conductors and magnetic cores, so a good physics explanation often has to separate them clearly.

## Connections

### Magnetic Hysteresis

This is the specific form of hysteresis that appears in ferromagnetic materials. The magnetization depends on the field history, which is why the graph forms a loop instead of a single line. If you are working on magnetic materials, this is the version you usually mean.

### Eddy Currents

Eddy currents are circulating currents induced in conductors by changing magnetic flux. They also waste energy, but through current flow and resistive heating rather than domain lag. In many devices, hysteresis and eddy current losses appear together, so it helps to tell them apart.

### Energy Loss

The area inside a hysteresis loop represents energy lost per cycle. In Physics II problems, that means you are often reading a graph to infer efficiency or heating, not just describing magnetism. Bigger loops mean more lost energy.

### [flux linkage](/principles-physics-ii/key-terms/flux-linkage)

Flux linkage tracks how magnetic flux connects with a circuit or coil. Hysteresis changes the magnetic state of a core, which can change the flux linked to a coil even when the external field is being reduced. That history dependence affects induced EMF in real setups.

## On the AP Exam

A quiz or problem set might give you a B versus H graph and ask you to identify the hysteresis loop, the remanent magnetization, or the coercive field. You may also be asked to interpret the area of the loop as energy lost per cycle or compare two core materials for efficiency.

In a lab, you might watch a ferromagnetic sample being cycled through increasing and decreasing magnetic fields and record the loop shape. The task is usually to explain why the curve does not retrace itself, then connect that result to heating, residual magnetism, or device performance. If the question mentions transformers, motors, or magnetic storage, hysteresis is often part of the reasoning.

## Hysteresis vs Eddy Currents

Students often group hysteresis and eddy currents together because both cause energy loss when magnetic fields change. They are not the same mechanism, though. Hysteresis comes from the delayed response of magnetic domains inside a material, while eddy currents are actual induced currents flowing in conductive material. Both can heat a device, but they show up differently in graphs and explanations.

## Key Takeaways

- Hysteresis is the lag between a changing field and a material’s response, and in magnetism it shows up as a loop on a graph.
- A magnetic material can keep some magnetization after the external field is removed, which is why hysteresis includes residual magnetism.
- The area inside the hysteresis loop represents energy lost per cycle, usually as heat inside the material.
- Low-hysteresis materials are preferred when you want efficiency, especially in transformers, motors, and other changing-field devices.
- Hysteresis depends on the material’s history, so the current state is not determined by the applied field alone.

## FAQs

### What is hysteresis in Principles of Physics II?

Hysteresis is the lag between an applied magnetic field and the magnetization of a material. In Physics II, it shows up when a ferromagnet does not return along the same path as the field is reduced. That difference creates a loop on the graph and signals energy loss.

### What does the hysteresis loop mean?

The hysteresis loop shows that magnetization depends on the material’s past, not just the current field. Its shape lets you identify remanence, coercive field, and energy lost per cycle. The bigger the loop area, the more energy is wasted as heat.

### How is hysteresis different from eddy currents?

Hysteresis is caused by the delayed realignment of magnetic domains. Eddy currents are loops of electric current induced inside a conductor when magnetic flux changes. They can both cause heating, but they come from different physical processes.

### Why do transformers use materials with low hysteresis?

Transformers work best when the core can magnetize and demagnetize with very little energy loss. A low-hysteresis material has a smaller loop area, so less energy turns into heat each cycle. That improves efficiency and reduces unwanted warming.

## Related Study Guides

- [7.5 Eddy currents](/principles-physics-ii/unit-7/eddy-currents/study-guide/4pPuONFwGG7DfhSS)

## About This Document

Canonical Fiveable pages are available as Markdown at the same path plus `.md`.

- [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns
- [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing
- [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`)
- [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`)

## Structured Data

```json
{"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/principles-physics-ii/key-terms/hysteresis#resource","name":"Hysteresis in Principles of Physics II","url":"https://fiveable.me/principles-physics-ii/key-terms/hysteresis","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/principles-physics-ii/key-terms/hysteresis#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:23:58.482Z","isPartOf":{"@type":"Collection","name":"Principles of Physics II Key Terms","url":"https://fiveable.me/principles-physics-ii/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/principles-physics-ii/key-terms/hysteresis#term","name":"Hysteresis","description":"Hysteresis is the lag between an input and a system’s response. In Principles of Physics II, it shows up most clearly in magnetic materials, where magnetization does not retrace the same path as the applied field.","url":"https://fiveable.me/principles-physics-ii/key-terms/hysteresis","inDefinedTermSet":{"@type":"DefinedTermSet","name":"Principles of Physics II Key Terms","url":"https://fiveable.me/principles-physics-ii/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is hysteresis in Principles of Physics II?","acceptedAnswer":{"@type":"Answer","text":"Hysteresis is the lag between an applied magnetic field and the magnetization of a material. In Physics II, it shows up when a ferromagnet does not return along the same path as the field is reduced. That difference creates a loop on the graph and signals energy loss."}},{"@type":"Question","name":"What does the hysteresis loop mean?","acceptedAnswer":{"@type":"Answer","text":"The hysteresis loop shows that magnetization depends on the material’s past, not just the current field. Its shape lets you identify remanence, coercive field, and energy lost per cycle. The bigger the loop area, the more energy is wasted as heat."}},{"@type":"Question","name":"How is hysteresis different from eddy currents?","acceptedAnswer":{"@type":"Answer","text":"Hysteresis is caused by the delayed realignment of magnetic domains. Eddy currents are loops of electric current induced inside a conductor when magnetic flux changes. They can both cause heating, but they come from different physical processes."}},{"@type":"Question","name":"Why do transformers use materials with low hysteresis?","acceptedAnswer":{"@type":"Answer","text":"Transformers work best when the core can magnetize and demagnetize with very little energy loss. A low-hysteresis material has a smaller loop area, so less energy turns into heat each cycle. That improves efficiency and reduces unwanted warming."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Principles of Physics II","item":"https://fiveable.me/principles-physics-ii"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/principles-physics-ii/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 7","item":"https://fiveable.me/principles-physics-ii/unit-7"},{"@type":"ListItem","position":4,"name":"Hysteresis"}]}]}
```