Magnetic Field Visualization
Field Parameters
Magnet Properties
Display Options
Visualization Options
Quick Presets
Magnetic Field Formulas
Instructions
- Drag magnets to change position
- Use dropdown to switch magnet type
- Adjust sliders to change field parameters
- Observe compass needles aligning with field
- Field lines emerge from N pole and return to S pole
What is a Magnetic Field?
A magnetic field is a physical field surrounding magnetic materials and moving electric charges, which exerts force on other moving charges and magnetic materials. Magnetic field lines are used to visualize the field - their direction shows the field direction, and their density indicates field strength. Outside a magnet, field lines emerge from the N pole and return to the S pole; inside the magnet, they flow from S to N, forming closed loops.
Bar Magnet
A bar magnet is the most common form of magnet, with N (north) and S (south) poles at opposite ends. Magnetic field lines are densest near the poles, indicating the strongest field; they are sparser in the middle region, indicating a weaker field. Like poles repel each other, while opposite poles attract.
Horseshoe Magnet
A horseshoe magnet concentrates both N and S poles at one end, creating a strong magnetic field in a small space. This shape is commonly used in applications requiring strong fields, such as electromagnetic cranes and speakers. Magnetic field lines are primarily concentrated between the two poles.
Properties of Magnetic Field Lines
Magnetic field lines have several important properties: (1) They are closed loops that never intersect. (2) The tangent to a field line at any point gives the direction of the magnetic field at that point. (3) The density of field lines is proportional to the magnetic field strength. (4) Outside a magnet, field lines emerge from the N pole and return to the S pole; inside, they flow from S to N. (5) The direction of field lines indicates the direction of force on a north magnetic pole.
Compass Needles and Navigation
A compass needle experiences magnetic torque in a magnetic field, causing its N pole to align with the field direction. Compasses use this principle to indicate direction. Earth itself acts as a giant magnet, with Earth's magnetic field causing compass N poles to point toward geographic north (near the magnetic south pole). The magnetic poles do not perfectly align with geographic poles, creating a magnetic declination.
Earth's Magnetic Field
Earth's magnetic field resembles that of a bar magnet, with the magnetic axis inclined about 11.5° from Earth's rotational axis. The magnetic south pole is near geographic north, and the magnetic north pole is near geographic south. Earth's magnetic field protects the planet from solar wind and cosmic rays, making it essential for life. Magnetic declination is the angle between true north (geographic) and magnetic north (compass).
Applications
Magnetic fields and magnets have numerous applications: compass navigation, electric motors and generators, electromagnetic cranes, maglev trains, magnetic resonance imaging (MRI), magnetic storage devices (hard drives, tapes), speakers, magnetic sensors, scientific research, and medical equipment.