--- title: "Magnetic Fields" description: "Describe magnetic poles (north and south), explain attraction and repulsion between poles, describe magnetic field lines plotted using a compass, and explain the Earth's magnetic field and its practic" canonical: https://lightmysky.com/learn/science/magnetic-fields-mt_56aspHjU19 source: https://lightmysky.com/learn/science/magnetic-fields-mt_56aspHjU19.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Magnetic Fields Describe magnetic poles (north and south), explain attraction and repulsion between poles, describe magnetic field lines plotted using a compass, and explain the Earth's magnetic field and its practical uses Subject: Science · Area: Forces & Motion · Ages 11 to 12 Page: https://lightmysky.com/learn/science/magnetic-fields-mt_56aspHjU19 ## Ready when they can - States the rule for attraction and repulsion of magnetic poles - Draws the magnetic field pattern around a bar magnet from memory or compass readings - Explains why a compass needle points north - Explains that the Earth has a magnetic field and describes how it is used for navigation ## Lesson: Magnetic Fields You have met north and south magnetic poles. Like poles repel, or push apart. Opposite poles attract, or pull together. A magnetic field describes magnetic effects in the space around a magnet. It has a strength and a direction. Magnets can also attract unmagnetised iron. A compass needle is a tiny magnet free to turn. Its north tip follows the combined field; its south tip points the other way. A strong nearby magnet can dominate Earth's field. Just beyond a bar magnet's north end, in line with the bar, the north tip points away. Beyond its south end, it points toward the magnet. To map direction, place a compass, mark its north-tip direction, move it and repeat. *(drawing: This shows the mapping procedure, not the curved field pattern.)* Field lines are drawing tools, not real threads. Outside a bar magnet, draw curved paths from north to south, bowing around both sides. Inside, the paths return south to north, making loops. Lines cannot cross: that would give two field directions at one point. Iron filings show the pattern but not arrow direction. View a sealed filings display with an adult. *(drawing: These words trace a loop. They do not draw its curved shape.)* On a map drawn to show strength, closer field lines mean a stronger field. A bar magnet's field is strongest near its poles. A field sensor measures strength; compass swing speed is not a reliable measure. With the magnet fixed and other fields negligible, moving directly outward from a pole lowers the reading. Halving distance does not generally double field strength. **Example.** Mia measures 12 units at A near a pole and 5 units at B farther out. Subtract to find the drop: 12 minus 5 is 7 units. Double a reading only if told it doubles: twice 6 is 12. To count direction readings, add each group once. Two near each pole and three along the sides make 2 plus 2 plus 3, or 7 readings. *(drawing: These are given strength readings. Compass directions alone do not supply these numbers.)* Earth has a magnetic field. Its broad pattern resembles a bar magnet's field, but no giant solid bar magnet is buried inside Earth. Away from magnetic objects, a compass's north tip usually points roughly toward geographic north. It need not point exactly north, and near Earth's magnetic poles it can be unreliable. Without Earth's field or any other magnetic field, a compass would have no magnetic reason to choose north. A compass helps you navigate by showing direction. Clockwise, its directions are north, east, south and west. Each is a quarter-turn from the next. Facing north, east is on your right. Magnets, speakers and steel objects can disturb a reading. Move away, let the needle settle, then read the compass before choosing your route. *(drawing: Take a reading away from objects that disturb the compass.)* Imagine a bar magnet divided across its middle. Each piece still has a north pole and a south pole, with its own field. Dividing the bar does not separate the two types of pole. This is a thought experiment, not an instruction to snap a magnet. **Recap.** Field lines form loops. Outside a bar magnet they point north to south. Compasses show field direction, sensors measure strength, and Earth's field helps us navigate. *The lesson, questions and flashcards were written for this dataset. OpenStax College Physics was consulted for facts about magnetic fields, poles and compasses.* ## Practice 28 questions on this page, each with its working shown. ## Needs first - [Magnetic Poles](https://lightmysky.com/learn/science/magnetic-poles-mt_jgNB2752b9) ## Opens up - [Electromagnets](https://lightmysky.com/learn/science/electromagnets-mt_2qkn8Lhc8e)