Domain: Natural Science — Physics
Target concept: Iron filings align around a bar magnet when the surface is gently struck.

Video generation prompt: Place a bar magnet under a piece of paper on a table, sprinkle iron filings on the paper, and then gently tap the paper from the side while keeping the magnet stationary.

Evaluation guide:
(i) Target concept: Visualization of static magnetic field lines via ferromagnetic particle alignment.
Minimum mechanism: Iron filings must be unmagnetized initially; bar magnet must generate a stable dipole field; tapping must provide kinetic energy to overcome static friction so filings can rotate into field-aligned orientation; paper must constrain filings to 2D plane for clear pattern formation.
(ii)Storyline: [Phase 1] Static setup: magnet fully occluded under flat paper, filings randomly distributed on paper surface. [Phase 2] Trigger: side-tap applied to paper edge → induces transient vibration. [Phase 3] Response: filings rotate and translate minimally to align along local field direction, forming connected pole-to-pole chains. [Phase 4] Stabilization: alignment persists after vibration ceases. Perspective must be overhead or slight oblique (≤30°), maintaining full visibility of paper surface and filing pattern; no occlusion of paper area between poles; magnet location inferred solely by filing geometry, not direct view.

Manual:
Experimental Procedure
1. Place a bar magnet flat under a plain sheet of paper on a stable table.
2. Evenly sprinkle iron filings over the entire paper surface.
3. Gently tap the side edge of the paper once — keeping magnet stationary.
Observation of Experimental Phenomena
Iron filings rapidly align into distinct curved lines connecting the two poles of the magnet, forming a visible dipole magnetic field pattern.
Summary of Experimental Principles
Iron filings are ferromagnetic and become induced magnets when exposed to a magnetic field; their alignment reveals the direction and shape of magnetic field lines around a bar magnet.

Prompt Grounding rubric:
level_1: No paper is placed on the table, no iron filings appear anywhere, and no tapping action occurs; the paper shows no indication of a magnet concealed beneath it; none of the four required elements (a magnet implied under the paper, sheet of paper, iron filings, table) appear together in a coherent setup.
level_2: At least one required element appears (e.g., paper or iron filings on the table), but nothing about the setup (paper position, later filing alignment) is consistent with a magnet resting under the paper, or the tap is directed at the wrong object (e.g., an exposed magnet or the table itself instead of the paper), or filings are shown but never sprinkled onto the paper surface, or the magnet itself is shown exposed/uncovered at any point in the clip.
level_3: A flat sheet of paper rests on a table with a bar magnet already in place underneath it from the start (never shown being placed or uncovered), iron filings are sprinkled onto the paper surface, and a side-tap is applied to the paper's edge rather than to the magnet or table directly; all elements appear in this configuration, but the order is wrong (e.g., the tap occurs before the filings are sprinkled) or a required action is skipped (e.g., filings appear already sprinkled with no visible sprinkling motion).
level_4: The bar magnet is implied to be centered under the paper rather than off to one side or exposed at an edge, the iron filings are sprinkled across the whole paper surface with none spilled onto the bare table before tapping begins, and the tap is delivered by a finger or handheld object making contact at the paper's side edge, with the magnet already concealed in place at the start and sprinkling then tapping occurring in that correct order; one non-core flaw exists, such as the tapping implement being ambiguous or one corner of the paper not being visible in frame.
level_5: Everything required at the 4-point level holds, and in addition the magnet is never directly shown on screen at any point (its presence is inferable only from the paper's placement over it), the tap is unambiguously delivered from the side of the paper rather than from above, and no extraneous object (a second hand, a tool, on-screen text) blocks the view of the paper surface where the filings sit.

Scientific and Causal Correctness rubric:
level_1: The iron filings show no alignment at any point; they remain randomly scattered before, during, and after tapping, or behave as inert powder that simply settles, clumps uniformly, or scatters chaotically with no relation to the magnet's position.
level_2: The filings move when tapped but never form any connected linear or curved structure; any pattern that appears contradicts a dipole field (e.g., filings form concentric circles, radiate outward from a single point, or settle into a uniform grid), or filings merely pile up at the magnet's ends without any strand extending between them.
level_3: The filings form separate, broken line segments that run between the two ends of the magnet, denser near the ends, tracing curved paths consistent with a bar magnet's dipole field; the segments do not cross each other or form closed loops unrelated to the magnet's orientation, and none of the filings align perpendicular to the pole-to-pole axis.
level_4: The filings form broken-but-directional segments between the poles as described above, and additionally the alignment only appears once tapping begins (the filings are randomly scattered beforehand), and the resulting pattern holds its shape once tapping stops, with every aligned segment running from one pole toward the other rather than in unrelated directions.
level_5: The filings form continuous, unbroken chains linking one pole of the magnet to the other, with no visible gaps interrupting a chain's path (no gap wider than roughly one filing's length); the chains curve smoothly and are roughly mirror-symmetric about the magnet's long axis; once the pattern has settled after tapping, no stray filings sit outside the chains, and the pole-to-pole connection is visually unambiguous across the whole pattern.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal break: the magnet appears to jump to a new position under the paper with no visible cause, the paper visibly tears or folds in a way inconsistent with a gentle tap, iron filings disappear from one frame and reappear elsewhere, the overall scene lighting shifts in a way inconsistent with a single continuous light source, or the camera cuts to a completely different viewpoint with no transition.
level_2: Multiple smaller inconsistencies: a shadow on the paper jumps to a different position between frames with no corresponding light or object change, iron filings appear to jitter or shift on their own between taps with no visible cause, the magnet's position under the paper shifts slightly between frames with no visible tap or nudge causing it, or the paper's edge moves inconsistently with the force and direction of the tap shown.
level_3: The magnet's position and orientation under the paper stay fixed for the whole video; the paper stays flat and still except for a brief, localized vibration exactly at the moment of each tap; the iron filings move only in direct response to a tap and never drift or shift on their own between taps; no object disappears, reappears, or jumps position without a visible cause.
level_4: In addition to the fixed magnet position and filings that move only when tapped, the paper's response to each tap is a small, localized ripple or vibration rather than the whole sheet shifting or sliding on the table; the filings settle into new positions only during and immediately after each tap rather than continuing to creep afterward; there is no flickering or doubled/ghosted appearance of the filings between consecutive frames.
level_5: Camera framing, lighting, and object positions remain consistent from the first frame to the last: the magnet's position under the paper never changes, the paper's only motion is the brief localized vibration at each tap, and the filings' movement begins immediately and visibly at the moment of contact with no perceptible delay after the tap, with their new resting positions remaining stable and consistent frame-to-frame once each tap's vibration has settled.