Magnetic Field Mapping - Physics Demonstrations - Magnetic Field Mapping | Physics Undergraduate Labs

Purpose

Small compasses placed around bar magnets reveal the direction of the magnetic field at discrete points, mapping out field line patterns. Students observe the vector nature of $\vec{B}$ , the dipole field topology, and superposition when multiple magnets are present.

Ten silver-cased compasses with red cardinal direction markings arranged in a circle around a black-and-red bar magnet labeled N and S on a white surface

Twelve clear-cased compasses with blue-and-black needles arranged in an oval pattern around a black-and-red bar magnet labeled N and S on a white surface

Ten silver-cased compasses clustered near the red S-pole end of a bar magnet on a white surface

Thirteen compasses in a grid pattern around two small red-and-blue bar magnets placed side by side in the center on a white surface

Thirteen compasses in a grid pattern around a single small red-and-blue bar magnet in the center on a white surface

Figure 1: Compasses positioned around a bar magnet show the magnetic field direction at various points, with needles aligning tangent to field lines radiating from the magnet's poles.

Figure 2: Alternative compass arrangement demonstrating the radial-to-circular field pattern around a bar magnet, useful for showing field topology without cardinal direction markings.

Figure 3: Close-up view showing detailed compass needle orientations near one magnetic pole, emphasizing the stronger field gradients and tighter field line spacing near the pole surface.

Figure 4: Symmetrical compass array with two bar magnets demonstrates superposition of magnetic fields, allowing investigation of field patterns for different magnet orientations and separations.

Figure 5: Grid arrangement optimized for document camera viewing, showing how compass positions can systematically map field topology for quantitative analysis of field patterns.