Magnetic Fields and Forces Topic

Magnetic Fields

Concept 6 demos

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

Magnetic Field Mapping

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, the dipole field …

Tangent galvanometer with large vertical circular coil on wooden base, compass with colored hemisphere markers at center, connected via red cables to a DC power supply reading 02.0V and 00.0A

Tangent Galvanometer

Demonstrates that current-carrying conductors produce magnetic fields by showing the deflection of a compass needle at the center of a coil. The deflection angle reveals the superposition of the coil's …

PASCO Scientific dip needle (Model SF-8619) with white rectangular base, black vertical post and horizontal arm supporting a transparent circular protractor with copper-colored magnetized needle

Dip Needle

Demonstrates the three-dimensional nature of Earth's magnetic field by measuring the magnetic inclination (dip angle). Students see that the field has a substantial vertical component at mid-latitudes, not just the …

Fields and Currents

Concept 4 demos

Top: Blue variable transformer (rheostat), Elenco PE-20 DC power supply (battery eliminator), red connecting leads, and jar of iron filings on a lecture bench. Bottom: Five electromagnetic slides in black frames with different conductor configurations — straight wire, loop, coil, and solenoid cross-sections — with red banana plug connectors.

Electromagnetic Slides

Iron filings on transparent slides reveal magnetic field patterns around various current-carrying conductor geometries (straight wire, loop, coil, parallel wires), projected for the class via overhead projector. Students see direct …

Overhead projector image of four miniature compasses arranged around the vertical conductor wire, all needles aligned in the same direction

Field around a Conductor

Miniature compasses around a vertical current-carrying wire show the circular magnetic field pattern predicted by Ampere's Law. Students observe field direction reversing with current direction (right-hand rule) and field strength …

Solenoid slide on overhead projector stage with battery eliminator power supply and blue Variac transformer on the bench, connected with red banana cables

The Magnetic Field of a Solenoid

Iron filings on an overhead projector reveal the magnetic field pattern of a current-carrying solenoid. Students observe parallel field lines inside the coil and a dipole pattern outside, connecting the …

Forces on Magnets

Concept 1 demo

Two vertical wooden rods on a wooden base. Left rod: ceramic ring magnets levitating with visible gaps, binder clip at top. Right rod: darker rare earth ring magnets stacked with less separation.

Magnetic Levitation

Demonstrates magnetic repulsion and force equilibrium by stacking ring magnets with like poles facing on vertical rods. Comparing ceramic and rare earth magnets side by side shows how material properties …

Force on Moving Charges

Concept 4 demos

Hand holding a magnet against a color CRT monitor screen, producing dramatic swirling rainbow distortion of the test pattern image

CRT Monitor in Magnetic Field

A strong magnet visibly distorts the image on a color CRT monitor by deflecting the electron beams via the Lorentz force. Students observe the cross-product relationship between field direction, electron …

Complete setup: Xantrex power supply (4.35 V, 0.5 A) connected to a wooden induction coil box, which drives a Crookes tube on a wooden stand showing a straight green electron beam; red-and-black bar magnet rests on the table below

Electron Beam Tube

A visible electron beam in a Crookes tube deflects when a bar magnet is brought near, directly demonstrating. Approaching from different directions shows the cross-product geometry and confirms the sign …

e/m apparatus: large Helmholtz coils on a stand with e/m tube (wrapped in dark shielding) at center, multiple power supplies and meters on a wooden table in a lecture hall

e/m Experiment

Electrons accelerated through a known potential are deflected into circular paths by Helmholtz coils, enabling direct measurement of. Demonstrates the Lorentz force on moving charges and connects to Thomson's discovery …

Force on Current in Wires

Concept 3 demos

Two long black rubber-insulated wires hanging from a wooden clamp on a vertical support rod, with a white paper backdrop behind them, a red Optima 12V battery and switch on the bench below, and heavy orange leads connecting the circuit

Force on Parallel Conductors

Shows the magnetic force between parallel current-carrying wires: parallel currents attract, antiparallel currents repel. A fiber optic lamp projects wire shadows onto a white backdrop so the motion is visible …

Clamp stand on lecture bench with red wire hanging from horizontal rod, radar magnet on its side at edge of bench, Energizer battery and telegraph switch connected via red wires

Jumping Wire

Demonstrates the Lorentz force on a current-carrying wire in a magnetic field. Students apply the right-hand rule to predict the wire's motion, then verify by reversing current polarity.

Xantrex DC power supply set to 8V, connected via leads to a mounted DPDT switch (left) and the conductor-axle apparatus on a wooden base with metallic rails and permanent magnet assembly (right)

Ampere's Motor

A current-carrying axle rolls along conducting rails in a magnetic field, demonstrating. A DPDT switch reverses current direction, reversing the force — a direct illustration of the right-hand rule and …

Torques on Coils

Concept 5 demos

Leeds and Northrup ballistic galvanometer: black metal housing with front window showing internal mirror and coil assembly, manufacturer label with specifications, suspension tube extending from top, mounted on three-legged cast iron base with brass leveling screws

Leeds and Northrup Ballistic Galvanometer

Illustrates the moving-coil galvanometer principle: current through a suspended coil in a magnetic field produces torque, deflecting a mirror whose rotation is read optically. A historical example of precision analog …

Welch galvanometer with black metal casing, semicircular scale marked -5 to +5, open window showing internal coil mechanism, schematic diagram on face, and binding posts on front panel

Welch Lecture Table Meter

Demonstrates the operating principle of a d'Arsonval (moving-coil) galvanometer. The open construction allows students to see the coil, magnet, and suspension while the schematic on the dial face illustrates the …

Wire coil suspended between poles of a horseshoe magnet on a wooden base, connected via red wires to a Xantrex DC power supply reading 3.17 V

Current Loop in Magnetic Field

A current-carrying coil suspended in a horseshoe magnet's field rotates to align with the field, demonstrating the torque on a magnetic dipole. Students observe the motor principle: magnetic forces on …