Domain: Natural Science — Physics
Target concept: U-shaped iron core of a current-carrying coil for attracting iron filings

Video generation prompt: On the table, a copper coil is wound around one leg of a U-shaped iron core and energized, while iron filings are sprinkled on the iron core and air gap, followed by de-energization.

Evaluation guide:
(i) Target concept: Magnetic field visualization via iron filings in a current-carrying U-core electromagnet.
Minimum mechanism: Iron filings must be ferromagnetic and respond to field gradients; U-core must provide low-reluctance path; air gap must exist to force field extension; coil current must be sufficient to saturate core locally; de-energization must remove field entirely to allow filings to lose alignment.
(ii)Storyline: Phase 1 (Energized): Static shot of setup → visible alignment of filings along core and across gap → stable bridging chain confirmed. Phase 2 (De-energized): Same frame → immediate and global collapse of all aligned structures → filings revert to isotropic scatter. Perspective: Fixed frontal/slightly elevated view showing full U-core, one-coil leg, and air gap; no occlusion; all key regions (core surface, gap, filings) fully visible and in focus throughout.

Manual:
Experimental Procedure
1. Place U-shaped iron core horizontally on table.
2. Wind copper coil tightly around only one leg of the core.
3. Energize coil (e.g., connect to power source).
4. Sprinkle iron filings evenly over the entire core surface and across the air gap.
5. Observe filings align along the core and bridge the air gap.
6. De-energize coil.
7. Observe filings collapse into disordered heaps.
Observation of Experimental Phenomena
When energized: iron filings align along magnetic path — forming continuous lines from pole to pole and bridging the air gap as an unbroken chain. When de-energized: filings collapse into disordered heaps with no alignment or bridging.
Summary of Experimental Principles
Current in coil magnetizes U-shaped iron core, creating north and south poles at ends of legs. Magnetic field concentrates in iron and crosses air gap, attracting and aligning iron filings along field lines.

Prompt Grounding rubric:
level_1: The U-shaped core, the copper coil, or the iron filings is entirely missing from the shot, the coil is not shown wound on the core at all, or the video never shows any moment where the coil is distinguishably energized versus de-energized.
level_2: The U-core, coil, and filings are all present and some visual cue distinguishes energized from de-energized, but the coil is wound around both legs (or in a way clearly not confined to one leg), or the filings sit only on the table around the core rather than on the core surface and across the air gap.
level_3: The U-shaped core rests on the table with the copper coil wound around exactly one leg; iron filings cover the core's surface and the air gap between the two leg ends; two distinct moments are shown, one with the coil connected to a power source (energized) and one with it disconnected (de-energized), with a visible cue such as a switch position or a wire being connected or removed.
level_4: All of score 3, plus the copper coil is visually distinct in color from the gray core and the dark filings, the coil sits on the leg nearest the air gap as described in the prompt, the filings are distributed across both the core surface and the gap, and the energized moment is shown before the de-energized moment, matching the prompt's order.
level_5: All of score 4, plus the coil never appears on the second leg or crosses over itself, no filings appear scattered on the table outside the core's footprint, and the camera framing, lighting, and distance stay the same between the energized and de-energized shots so the two moments can be compared directly.

Scientific and Causal Correctness rubric:
level_1: The filings never form any chain in either the energized or de-energized shot, or a chain that formed while energized is still fully intact after the coil is de-energized.
level_2: The filings shift or clump somewhat once the coil is energized, but they never form a continuous chain bridging the air gap, or the visible difference between the energized and de-energized shots is too small to tell that the current made a difference.
level_3: While the coil is energized, the filings form a visible chain running from one leg end, across the core, to the other, and this chain bridges the air gap; once the coil is de-energized, that chain breaks apart into a loose, random heap with no bridging remaining.
level_4: All of score 3, plus the aligned filings stay confined to the core surface and the gap (none of them line up in open air beyond the gap's edges), and after de-energizing, no partial chain or bridge is left over the gap.
level_5: All of score 4, plus the filing chain is visibly denser near the two leg ends and thinner along the middle of each leg, the bridge across the gap runs straight rather than sagging or fanning out, and the whole chain collapses at essentially the same moment the coil is de-energized rather than settling gradually afterward.

Spatiotemporal Consistency rubric:
level_1: The core, coil, or filings appear or disappear abruptly between frames, the coil's winding changes shape or position with no visible cause, the core or coil visibly morphs, stretches, or is clipped from one frame to the next, or the lighting flips between bright and dark with no corresponding event on screen.
level_2: Filings jump from one location to another with no visible in-between motion, the core or coil drifts or rotates without a smooth transition, the air gap's width changes from one frame to the next with nothing shown to cause it, or the table surface visibly flickers or warps.
level_3: The core stays in the same place on the table, the coil stays wound on the same leg, and the air gap keeps the same width throughout; filings only move in ways tied to a visible cause (sliding into alignment while energized, or falling into a heap once de-energized) with no filing disappearing or resizing without reason.
level_4: All of score 3, plus the filings' alignment builds up gradually across several frames rather than snapping into place instantly, the collapse after de-energizing happens as one connected motion rather than in disconnected bursts, and no filing appears to sit inside the core material or float unsupported above the gap.
level_5: All of score 4, plus the camera holds one fixed position with no pan, tilt, or zoom, the core, coil, and filings keep a consistent relative perspective with no parallax drift, and the filings never appear to pass through the coil's wire loops as they move.