Part 08 · Circuits and magnetism · Card 8 of 12
Magnetic field
A region where moving charges and magnets feel force. Measured in tesla. Field lines form closed loops.
Last updated
Analogy
An invisible landscape that a compass needle follows.
Example
Field size
Earth: 5e-5 TFridge magnet: 5e-3 TMRI scanner: 1.5 T
In practice
Earth's magnetic field is about 5e-5 T. A fridge magnet is about 5e-3 T.
Practice
Flashcards
- What is the SI unit of magnetic field?The tesla (T).
Questions people ask
Can you have a magnet with only one pole?
No one has ever found one. If you cut a bar magnet in half, you get two smaller magnets, each with a north and south pole. Field lines have no start or end, so magnetic field lines always form closed loops.
What makes a magnet magnetic?
Spinning electrons inside atoms act like tiny magnets. In ordinary materials they point in random directions and cancel. In iron, groups of atoms called domains line up, so the effect adds up. A magnet has most domains pointing the same way.