Domain: Engineering — Electrical Engineering
Target concept: Experiment on the Voltage Law of Parallel Circuits

Video generation prompt: Two identical bulbs are connected in parallel. A voltmeter is used to measure the power supply voltage, the voltage across bulb L1, and the voltage across bulb L2. After closing the switch, observe the readings of the voltmeter for the three measurements.

Evaluation guide:
(i) Target concept: Voltage uniformity across parallel branches in a DC resistive circuit.
Minimum mechanism: Identical bulbs imply matched resistance; closed switch completes circuit; ideal voltmeter draws negligible current so does not alter branch voltages; power supply maintains constant output under load.
(ii)Storyline: Frame opens on complete parallel circuit with open switch → switch closes (bulbs ignite simultaneously) → voltmeter leads attach to supply terminals (stable reading appears) → leads detach and smoothly reattach to L1 terminals (same reading appears) → leads detach and smoothly reattach to L2 terminals (identical reading appears) → all bulbs remain lit continuously; entire sequence viewed from fixed frontal angle with full circuit in frame; no cuts, no zoom, no occlusion of terminals or digits during measurements.

Manual:
Experimental Procedure
1. Connect two identical bulbs L1 and L2 in parallel to a power supply. Close the switch.
2. Place voltmeter leads across power supply terminals → record reading.
3. Reposition leads across L1 terminals → record reading.
4. Reposition leads across L2 terminals → record reading.
Observation of Experimental Phenomena
- Both bulbs glow with identical brightness.
- Voltmeter displays the same non-zero voltage value in all three measurements.
Summary of Experimental Principles
- In a parallel circuit, voltage across each branch equals the supply voltage (V_total = V_L1 = V_L2).

Prompt Grounding rubric:
level_1: No parallel-circuit setup is visible: none of the two bulbs (L1, L2), the voltmeter, the switch, or the power supply appears anywhere in the frame.
level_2: A bulb and a voltmeter appear, but the wiring does not show L1 and L2 wired in parallel to a shared power supply, e.g., only one bulb is connected, or a wire is missing/disconnected; the switch is absent or not wired into the circuit.
level_3: Two visibly matching bulbs (L1, L2), one voltmeter, a switch, and a power supply are all present and wired in parallel; the voltmeter leads contact three distinct terminal pairs (the supply terminals, the L1 terminals, and the L2 terminals), but it is not clearly shown which pair the leads are on for at least one of the three measurements.
level_4: Everything required at the score 3 level is shown correctly, with L1 and L2 wired side by side to one shared power supply and the switch closed; the voltmeter leads are moved to the three terminal pairs in three visibly separate steps (supply first, then L1, then L2), each contact point unambiguous with no stray or incorrect connections.
level_5: Everything required at the score 4 level holds; in addition, L1 and L2 are identically styled (same size, color, bulb type); the leads are repositioned exactly three times, each new contact fully settled before the corresponding reading is shown; the framing each time isolates only the intended terminal pair under the leads with no other terminals partially in view; the order is strictly supply, then L1, then L2, with no step skipped or repeated.

Scientific and Causal Correctness rubric:
level_1: The voltmeter shows no legible or stable reading for one or more of the three measurements, or a reading that is physically inconsistent (e.g., the L1 or L2 reading exceeds the supply reading), or the bulbs stay dark even after the switch is closed.
level_2: The bulbs light up, but the voltmeter reads zero for all three measurements, or reads non-zero for only one of the three, or shows two visibly different non-zero values across the three measurements even though L1 and L2 are identical bulbs wired in parallel.
level_3: The bulbs stay lit; the voltmeter produces a legible, stable, non-zero reading for the supply, for L1, and for L2 in turn, and the three readings represent the same value (whether that is shown as matching numeric digits or as the same needle position/deflection angle), though nothing beyond the raw readings themselves signals that they are meant to be compared as equal.
level_4: Everything expected at the score 3 level holds; in addition, the three readings are shown in a directly comparable way each time (same display format and scale, no reformatting between measurements), none of the three readings changes or drifts once it appears, and both bulbs stay visually identical in brightness across all three measurements.
level_5: Everything expected at the score 4 level holds; in addition, the three readings are indistinguishable from one another on inspection (the same numeric value if the voltmeter is digital, or the same pointer position if it is analog), with no flicker, momentary jump, or gradual drift in any reading while it is being held on screen, and this equality coincides with all times the bulbs are shown lit.

Spatiotemporal Consistency rubric:
level_1: A bulb or the voltmeter vanishes and reappears, the leads jump directly from one terminal pair to another with no travel shown between, the scene switches from dark to fully lit within a single frame, or a wire appears severed and then whole again with no lead or hand ever touching it.
level_2: The leads move in visible skips (jumping ahead or briefly vanishing) instead of a continuous path between terminal pairs; bulb brightness flickers or changes unexpectedly between the three measurements; the background brightness or shadow direction shifts noticeably from one measurement to the next; the camera angle changes between the three lead placements with no cut shown.
level_3: The bulbs, voltmeter, switch, and power supply stay in the same positions relative to one another for the whole video; each time the leads move to a new terminal pair, they travel a continuous, visible path; both bulbs stay lit without dimming or flicker; the circuit board's brightness and shadow direction stay the same from the first measurement through the last; no wire, bulb, or voltmeter part bends or changes shape; the camera holds one fixed viewpoint that keeps the entire circuit in frame.
level_4: Everything expected at the score 3 level holds; in addition, the leads' movement always stays within the frame and is never cropped at an edge; the apparent spacing between the bulbs and the voltmeter terminals does not shift in a way that would suggest the camera itself moved; the wires never stretch, kink, or get hidden behind another part as the leads travel between terminal pairs.
level_5: Everything expected at the score 4 level holds; in addition, each lead repositioning moves in one steady direction without pausing, reversing, or overshooting the target terminal before settling; both bulbs hold one constant brightness level for the entire video; the shadows cast by the leads and wires on the circuit board keep pointing the same way throughout, consistent with a single unmoving light source; the bulbs, voltmeter body, and any visible labels stay aligned from frame to frame with no jitter a viewer could notice.