Domain: Natural Science — Physics
Target concept: Iron filings form magnetic field lines around a current-carrying circular wire.

Video generation prompt: A horizontally placed circular wire loop on a table is positioned beneath a transparent sheet. Iron filings are spread over the sheet; the current is then turned on, and later turned off.

Evaluation guide:
(i) Target concept: Magnetic field lines generated by a steady current in a circular loop are closed, concentric curves lying in planes perpendicular to the loop"s axis, with highest field strength near the wire and symmetric distribution about its center.
Minimum mechanism: Iron filings must be ferromagnetic, dry, and free to rotate; current must flow *only during* the alignment phase; sheet must be rigid and non-magnetic to avoid distortion; no external fields (e.g., Earth"s field) may dominate, ensured by horizontal wire + short duration + dominant local field.
(ii)Storyline: [Phase 1: Baseline] Static shot: horizontal circular wire on table, transparent sheet above it, iron filings uniformly scattered on sheet surface. [Phase 2: Trigger] Visual cue (e.g., illuminated switch) activates, no filing motion yet. [Phase 3: Causal Response] Filings begin rotating and migrating *only after cue*, forming continuous curved lines that encircle wire projection, increasing in density near wire edge. [Phase 4: Steady State] Pattern stabilizes: all curves closed, concentric, non-intersecting, symmetric about wire center. [Phase 5: Current Off] A second cue (e.g., switch dims) signals current has stopped; because dry filings resting on a rigid, horizontal sheet have no restoring force to re-scatter themselves once the field disappears, the aligned pattern is expected to persist largely unchanged for the remainder of the clip. The video is not required to show (and should not be penalized for omitting) an automatic snap-back to random dispersion absent some separate mechanical disturbance such as tapping the sheet. All phases occur from fixed overhead or slight oblique viewpoint ensuring full visibility of wire, sheet, and filing distribution; no occlusion; lighting remains constant.

Manual:
Experimental Procedure
1. Place a horizontal circular wire loop on a tabletop.
2. Position a transparent sheet flat and parallel above the wire.
3. Evenly spread dry iron filings over the transparent sheet.
4. Turn on electric current through the wire.
5. Observe filings rearrange into curved patterns.
6. Turn off current.
7. Observe that the curved pattern remains largely in place immediately after the current stops, since the filings rest passively on the sheet with no force pulling them back to random positions on their own.
Observation of Experimental Phenomena
Iron filings form continuous, closed, concentric curved lines centered on the wire’s projection — denser near wire perimeter, sparser toward center — once current flows through the loop; because the filings are simply resting on top of the sheet, this pattern persists after the current is switched off unless the sheet is physically disturbed (e.g., tapped) to redisperse them.
Summary of Experimental Principles
Current-carrying circular wire generates a magnetic field perpendicular to the plane of the loop; iron filings align along magnetic field lines, revealing their circular, symmetric structure around the wire.

Prompt Grounding rubric:
level_1: No circular wire loop is shown lying on the table; no transparent sheet appears above it; no iron filings are shown at any point; there is no visible cue for turning the current on or off.
level_2: Some core elements appear (a wire loop, a sheet, or filings), but they are not arranged as described: for example the wire is not circular or not lying flat on the table, the sheet is not positioned above the wire, or the filings are never shown resting on the sheet.
level_3: All three core objects are present in the right arrangement: a circular wire loop lies flat on the table, a transparent sheet sits directly above it, and iron filings are visible scattered on the sheet; a current-on cue (e.g., a switch, indicator light, or on-screen label) and a later current-off cue both appear at some point in the shot, though their exact timing relative to when the filings were scattered may be unclear.
level_4: Everything required at the 3-point level holds, and additionally: the filings are shown already spread across the sheet before the current-on cue occurs, matching the intended order (filings first, then current on, then current off); the current-on and current-off cues are each a single, distinguishable event rather than an ambiguous background change; no unrelated props clutter the shot.
level_5: Everything required at the 4-point level holds, and additionally: the current on/off cue is visually anchored near the wire or its power source (e.g., a switch or indicator placed at the wire's terminal) rather than floating disconnected from the setup; the wire, sheet, and filings all stay within a single continuous camera framing from the initial filing-spreading step through the final current-off cue, with no cut away from the setup at any point.

Scientific and Causal Correctness rubric:
level_1: Iron filings never form any curved or ring-like arrangement at any point in the clip: they stay randomly scattered regardless of whether the current is on or off, showing no visible interaction between the wire and the filings at all.
level_2: Filings do form some pattern, but it has no real causal tie to the current: for example the curved arrangement is already visible before the current is ever switched on, or the same arrangement stays on screen continuously whether the current is on or off, or the filings form straight lines, radial spikes, or random clumps instead of curves that trace around the wire.
level_3: A change in filing arrangement is at least loosely tied to the current cue (filings look more scattered before current-on and more organized into curve-like shapes afterward), but the resulting curves are imperfect: they may lack full rotational symmetry around the wire, or have a visible gap, crossing, or abrupt break in one of the curved lines.
level_4: Everything required at the 3-point level holds, and additionally: filings form continuous, non-crossing closed curves that encircle the wire's outline, denser near the wire and sparser away from it; this organized pattern is clearly absent before the current is switched on and clearly present once it is on. The pattern may persist for a while after the current is switched off without being penalized.
level_5: Everything required at the 4-point level holds, and additionally: filing density is visibly higher directly along the curved lines than in the gaps between them; the curves are evenly spaced and centered on the wire's own footprint (roughly symmetric about the wire's center, judged by eye) rather than skewed toward one side of the sheet; no organized curves are visible before the current switches on.

Spatiotemporal Consistency rubric:
level_1: The wire loop's position on the table suddenly changes from one moment to the next instead of staying put; the transparent sheet blinks out of the shot and back in; filings that were scattered in one moment appear rearranged into a totally different layout moments later with no visible motion shown in between; the lighting swings from bright to dark within a single cut; or the camera viewpoint abruptly switches (e.g., snapping from the overhead view to a side-on angle, or zooming suddenly) within the same shot.
level_2: The wire or sheet visibly warps, stretches, or changes shape rather than staying rigid; filings appear or disappear from the sheet with no visible sliding motion; shadows cast by the wire or filings jump to a new angle or vanish momentarily even though nothing in the room's lighting has changed; the edge of the table or other background elements shift shape or position partway through the clip.
level_3: Small rough edges are visible but nothing breaks badly: a few filings show a brief stutter as they slide into alignment, the wire's shadow is momentarily out of step with the sheet's shadow, but the filings never leave the sheet's surface and the wire never leaves the table.
level_4: Everything required at the 3-point level holds, and additionally: the wire stays rigid and in the same spot on the table throughout; the sheet stays flat and doesn't drift; filings move by visibly sliding or rotating into their curved arrangement rather than snapping straight into it; every shadow in the scene points the same way as every other shadow at a given moment, and that direction only shifts if something in the scene would plausibly cause it.
level_5: Everything required at the 4-point level holds, and additionally: each filing's motion looks like it is being drawn toward the wire's projection and settling into place, rather than every filing relocating all at once; no filing appears to pass through the sheet or the wire as if they were solid objects that don't interact; every filing's movement is consistent with gravity (none of them lift upward or float above the sheet).