Domain: Engineering — Electrical Engineering
Target concept: The pointer deflection of the analog voltmeter is greater when two batteries are connected in series than when a single battery is used.

Video generation prompt: On the desk, the red and black probes of an analog voltmeter are sequentially connected to a cylindrical battery, and then to a battery pack consisting of two identical batteries connected in series and secured together with tape.

Evaluation guide:
(i) Target concept: Voltage additivity in series-connected ideal DC sources.
Minimum mechanism: Batteries must be identical, non-depleted, and connected in true series (positive-to-negative); voltmeter must be analog, functional, and calibrated to respond linearly to voltage; internal resistance negligible relative to voltmeter impedance.
(ii)Storyline: Frame 1–3: Static wide shot showing voltmeter, single battery, and taped battery pack on desk, all fully visible, fixed viewpoint. Frame 4–6: Red probe contacts positive end of single battery; black probe contacts negative base; needle begins moving. Frame 7–8: Needle settles at first deflection position, held steady for ≥1 visual beat. Frame 9–11: Probes retract fully; no contact with any battery. Frame 12–14: Red probe contacts positive end of front battery in pack; black probe contacts negative end of rear battery; needle begins moving again. Frame 15–16: Needle settles at visibly farther position on same scale, held steady. No occlusion of needle or scale at any point; no change in camera or lighting.

Manual:
Experimental Procedure
1. Place analog voltmeter centered on desk.
2. Connect red probe to positive terminal and black probe to negative terminal of single cylindrical battery; observe needle.
3. Disconnect probes; reconnect them identically to positive terminal of first battery and negative terminal of second battery in taped-together series pack; observe needle.
Observation of Experimental Phenomena
The voltmeter needle deflects to a larger angle when connected to the two-battery series pack than when connected to the single battery.
Summary of Experimental Principles
Connecting identical batteries in series doubles the total voltage; analog voltmeter deflection is proportional to applied voltage.

Prompt Grounding rubric:
level_1: No analog voltmeter appears on the desk; no single cylindrical battery is shown; no taped pair of two identical cylindrical batteries is shown; the voltmeter's red and black probes never appear; the sequence of connecting to the single battery first and then to the two-battery pack is not shown.
level_2: The analog voltmeter is visible but its red and black probes are not both shown, or only one battery appears with no second battery or tape visible, or the probes never touch either battery, or the two-battery pack is contacted before the single battery.
level_3: The analog voltmeter with distinct red and black probes sits on the desk; a single cylindrical battery is shown; a taped pair of two identical cylindrical batteries (the series pack) is shown; the probes contact the single battery first, then the taped pack, in that visible order.
level_4: Everything required at the 3-point level is present, and both the single battery and the taped two-battery pack rest on the same desk within one fixed camera framing; the voltmeter's scale face stays fully visible during both probe contacts; the tape wrapped around the two-battery pack is clearly visible; no unrelated object blocks the voltmeter, probes, or batteries.
level_5: Everything required at the 4-point level is present, and the voltmeter stays stationary and facing the camera throughout; the red probe always touches the rounded positive cap and the black probe always touches the flat negative base, in both the single-battery and pack tests; the batteries are oriented the same way (positive cap up) in both tests; no probe, battery, or voltmeter appears, disappears, or is repositioned by an unseen cut between the two contacts.

Scientific and Causal Correctness rubric:
level_1: The needle does not move for either the single battery or the two-battery pack; or it deflects to the same angle for both; or it swings in the wrong direction (e.g., left instead of right from zero).
level_2: The needle deflects for both contacts but the two-battery pack does not produce a visibly larger deflection than the single battery; or only one of the two contacts produces any deflection; or the needle starts moving before the probes touch the battery or keeps moving after contact ends; or the needle overshoots and settles at an unstable, wavering position instead of a steady rest point.
level_3: The needle swings to a visibly larger angle when the probes touch the two-battery pack than when they touch the single battery; both deflections move in the same direction from the same zero mark; the needle comes to a stable rest in both cases.
level_4: Everything required at the 3-point level is present, and the two-battery deflection clearly passes at least one more major scale mark than the single-battery deflection; the needle returns fully to zero between the two tests; the zero position is the same before each test, showing no drift.
level_5: Everything required at the 4-point level is present, and the two-battery deflection angle is close to double the single-battery deflection angle measured from zero, matching the doubled voltage the series pair produces on a linear scale; the needle's motion during each contact is smooth and one-directional, without hesitation or backward swing; the needle and scale markings stay unobstructed and viewable straight-on during both readings.

Spatiotemporal Consistency rubric:
level_1: The voltmeter or a battery vanishes from one frame and reappears in another; the desk lighting suddenly changes with no visible cause; the voltmeter's face warps or stretches out of its normal shape; a probe tip disappears mid-motion instead of moving continuously; a battery rotates or slides with no probe or hand touching it.
level_2: The voltmeter jumps sideways by more than its own width between the two contacts; a probe tip appears in a new spot more than about 1 cm from where it last was, with no visible path connecting the two points; the tape on the two-battery pack appears or disappears between shots; a shadow on the desk swings to a new direction even though nothing on the desk has moved.
level_3: The voltmeter, single battery, and taped battery pack all stay in the same relative spots on the desk throughout; nothing warps, splits, or breaks apart; the desk lighting stays even in color and brightness across the sequence; each probe's approach to a battery is a continuous, gradual motion rather than a sudden jump; the voltmeter does not tip or rotate while a probe is touching a battery.
level_4: Everything required at the 3-point level is present, and additionally: the camera framing never pans, tilts, or zooms; the desk surface and its edge stay visibly steady with no drifting between frames; each probe's path from the single battery to the two-battery pack is unbroken and never passes behind another object.
level_5: Everything required at the 4-point level is present, and additionally: the motion across frames is fluid with no stutter, repeated frames, or strobing; no blocky smearing appears around the moving probe tips or the swinging needle; the voltmeter's casing and dial keep the same viewing angle throughout, with no tilting or stretching of its round face; the voltmeter's surface reflections stay constant with no flicker.