How do magnetic field lines work?

Magnetic field lines are continuous closed loops that emerge from the north pole and enter the south pole outside a magnet, and run from south to north inside it. They never cross each other, and their density indicates field strength — closer lines mean a stronger field.

What is the right-hand rule for magnetic fields?

For a straight current-carrying wire: point your right thumb in the direction of current flow, and your curled fingers indicate the direction of the magnetic field (circling the wire). For a solenoid: curl your fingers in the direction of current, and your thumb points toward the north pole.

How does a solenoid create a uniform magnetic field?

A solenoid is a tightly wound coil of wire. Inside the solenoid, the magnetic field contributions from each loop add together to create a nearly uniform field (B = μ₀nI, where n is turns per unit length). Outside, the field resembles that of a bar magnet and is much weaker.

Magnetic Field Visualizer

Explore magnetic fields from different sources. Switch between bar magnets, straight wires, wire loops, and solenoids to see field lines, compass needles, and iron filing patterns.

Field Parameters

Source

Strength = 5

Current = 10 A

Show

Field lines Compass needles Field vectors Iron filings

Properties

Source	Bar Magnet
Strength	5
Current	10 A
B at ref	--
Direction	--
Poles	--

The Physics Behind It

Magnetic Field Formulas

Straight wire: B = μ₀I/(2πr)
Solenoid: B = μ₀nI
Wire loop center: B = μ₀I/(2R)
Bar magnet: dipole field approximation
μ₀ = 4π × 10&sup7; T·m/A

Key Concepts

Magnetic field lines are always closed loops: they go from north to south outside the magnet and south to north inside
Right-hand rule: curl fingers in the direction of current, thumb points along the magnetic field
Solenoids produce a nearly uniform field inside, similar to a bar magnet externally
Field strength decreases with distance; for a wire it drops as 1/r, for a dipole as 1/r³

Magnetic Field Visualizer

Field Parameters

Properties

The Physics Behind It

Magnetic Field Formulas

Key Concepts

Related Visualizations

Electric Field

EM Induction

Polar Coordinates

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