Domain: Engineering — Electrical Engineering
Target concept: A vertical current-carrying wire causes the compass needle to deflect.

Video generation prompt: A straight conductor vertically passing through the table is connected to a direct current power supply; compasses are uniformly placed around the conductor. After the switch is closed, the battery connection direction is subsequently reversed.

Evaluation guide:
(i) Target concept: Magnetic field generated by steady direct current in a straight conductor is azimuthal (circular, centered on wire) and directionally reversible with current polarity.
Minimum mechanism: Current must flow axially through a straight conductor; compasses must be free to rotate horizontally in Earth"s weak background field; magnetic field strength must exceed local geomagnetic field enough to dominate needle alignment; no ferromagnetic interference nearby.
(ii)Storyline: Frame 0–2: Static setup, vertical wire through table, compasses evenly ringed, switch open, battery in initial orientation. Frame 3–4: Switch closure, immediate onset of simultaneous needle rotation. Frame 5–6: Stabilization, all needles locked in tangent positions. Frame 7: Battery reversal, visible swap of +/- connections. Frame 8–9: Second switch closure, immediate onset of simultaneous *opposite-direction* needle rotation. Frame 10: Final stabilization, all needles locked in reversed tangent positions. Perspective: Fixed overhead or slightly elevated frontal view, unobstructed line-of-sight to all compass cards and wire base; no occlusion of needle tips or pivot points.

Manual:
Experimental Procedure
1. A straight vertical wire passes through the center of a horizontal table.
2. Four or more identical compasses are placed evenly in a circle around the wire on the table surface.
3. The wire is connected to a DC power supply via a switch.
4. The switch is closed; observe compass needle orientations.
5. The battery terminals are reversed; the switch is closed again; observe new needle orientations.
Observation of Experimental Phenomena
All compass needles deflect simultaneously from north alignment to settle tangent to concentric circles centered on the wire. After battery reversal, all needles rotate in the opposite direction and settle in new tangent orientations.
Summary of Experimental Principles
A vertical current-carrying wire generates a circular magnetic field around itself. The direction of the field depends on current direction (right-hand rule). Compass needles align with the local magnetic field, thus tangentially encircling the wire.

Prompt Grounding rubric:
level_1: No vertical wire passing through the table is shown; or no compasses are visible; or no switch or battery is shown; or there is no depicted action of closing a switch or reversing the battery connections.
level_2: A vertical wire through the table and at least one compass are visible, but the compasses are not arranged in a ring around the wire (e.g., stacked together or placed only on one side), or no switch and battery are shown, or neither a switch-closing action nor a battery-reversal action is depicted.
level_3: A vertical wire passes through the table; at least three compasses are placed around the wire in a roughly circular arrangement; a switch and a battery are visibly connected to the wire; and the switch is shown being closed (e.g., a hand pressing it, or a visible toggle); but the battery-reversal action (swapping which terminal connects where) is never shown or cannot be identified.
level_4: A vertical wire passes through the table; four or more compasses are placed in a ring around the wire; a switch and battery are visibly connected; the switch is shown being closed once; and the battery-reversal action is also shown (e.g., two clearly different frames showing the terminal wires swapped, or a visible +/- label flip) followed by the switch being closed a second time; but one of these two switch-closing actions is unclear or too brief to confirm it happened.
level_5: A vertical wire passes through the table; four or more compasses are placed in a ring around the wire; a switch and battery are visibly connected; the switch is clearly shown being closed a first time; the battery terminals are then clearly shown reversed (two distinguishable connection states, before and after); and the switch is clearly shown being closed a second time after the reversal: every setup element and both switch-closing actions specified in the prompt are unambiguously depicted.

Scientific and Causal Correctness rubric:
level_1: The compass needles never move in response to the switch closing (all stay pointing north throughout), or they move but their final resting direction has no relation to which way the current flows (e.g., the same needle orientation appears both before and after the battery is reversed).
level_2: The compass needles move when the switch closes, but their final orientations are inconsistent with a field circling the wire, for example, different needles point in unrelated directions rather than all lying tangent to circles centered on the wire, or their rotation does not reverse when the battery polarity is reversed.
level_3: After the switch closes, the needles settle into directions tangent to circles centered on the wire, and after the battery is reversed and the switch closed again, the needles' resting directions visibly change, but it is not clear from the footage that the change is a full reversal (e.g., only some needles are shown after reversal, or the before/after orientations are too similar to confirm the reversal).
level_4: After the switch closes, all the visible compass needles settle into directions tangent to circles centered on the wire, consistent with a circular magnetic field around the current; after the battery is reversed and the switch closed again, all the needles rotate to new tangent directions that are clearly the reverse of their first orientation, but one or more needles show a resting direction that does not quite match the tangent-to-circle pattern expected at its position around the wire.
level_5: After the switch closes, every visible compass needle settles into a direction tangent to a circle centered on the wire, matching the circular magnetic field expected around a current-carrying conductor; after the battery polarity is reversed and the switch closed again, every needle rotates to the opposite tangent direction at its position, correctly reflecting the reversed current direction per the right-hand rule; the deflection pattern before and after reversal is consistent and unambiguous for every compass shown.

Spatiotemporal Consistency rubric:
level_1: The wire, the table, or a compass appears in a noticeably different position than in the previous frame with no motion shown getting it there, or one of them blinks out of the shot and back in with no visible cause; the table surface visibly tears or warps; the lighting in the scene flickers violently or casts shadows that are physically impossible for the setup shown; or the switch changes from open to closed with no visible press or motion.
level_2: The wire appears to bend or wobble when it should stay rigid and vertical; a compass needle's rotation skips or stutters between frames instead of turning smoothly; the view of the table shifts from looking straight down to an angled view partway through the clip; or the shadows in the scene point a different way with no lamp or camera movement shown to explain it.
level_3: The wire stays rigid and vertical, the table keeps the same flat surface and appearance, and each compass stays at the same position and distance from the wire throughout the clip; the needles turn smoothly from their starting orientation to their final resting direction with no skipped frames; and the overall brightness and shadow direction in the scene stay about the same except for any change tied to the switch action.
level_4: The wire, table, and every compass keep the same positions and spacing relative to one another for the whole clip; each needle's rotation is smooth and finishes close to when the switch or battery-reversal action happens rather than lagging far behind it; the compass dials and table edges never visibly warp; and the lighting and shadows change gradually rather than in sudden jumps.
level_5: The wire, table, and every compass keep exactly the same positions and spacing relative to one another for the entire clip with no drift or resizing; every needle's rotation is smooth and continuous from start to stop with no stutter, freeze, or sudden snap to a new angle; the switch-pressing motion looks like a natural hand or mechanical movement rather than an instant on/off change; and the lighting, shadows, and any reflections change gradually and consistently rather than jumping between states.