Domain: Engineering — Electrical Engineering
Target concept: Variation in the brightness of a bulb when batteries are added in series

Video generation prompt: A simple circuit composed of a small incandescent bulb and a single battery; another identical battery is subsequently connected in series while the bulb remains connected.

Evaluation guide:
(i) Target concept: Voltage additivity in series-connected ideal DC sources driving a resistive load.
Minimum mechanism: Bulb filament must behave as a temperature-dependent resistor whose luminance increases monotonically with applied voltage; batteries must be identical, non-depleted, and connected with correct polarity in series; no significant internal resistance effects visible at this scale.
(ii)Storyline: Frame 0–3s: Single battery connected to bulb → bulb lit at baseline brightness; Frame 4–6s: Second battery approaches first battery along axis aligned with terminals; Frame 7s: Metallic contact established between opposite terminals (pos→neg); Frame 8–10s: Bulb maintains continuous illumination with increased brightness: no interruption, no decay, no instability. Fixed frontal viewpoint; all objects fully visible; no occlusion; lighting environment neutral and stable.

Manual:
Experimental Procedure
1. Place a small incandescent bulb and a single AA/AAA battery in frame; connect them with a wire or direct metal contact to form a closed circuit.
2. Observe bulb illumination.
3. Introduce an identical second battery and connect it end-to-end (positive to negative) with the first battery, keeping the bulb connected to the free terminals.
Observation of Experimental Phenomena
The bulb glows dimly with one battery; after series connection of the second battery, the bulb glows noticeably brighter — same color, no flicker, no color shift.
Summary of Experimental Principles
Adding batteries in series increases total voltage across the bulb; higher voltage drives more current through the filament, increasing power dissipation and luminous output — consistent with Ohm’s Law and Joule heating.

Prompt Grounding rubric:
level_1: No bulb appears, or no battery appears, or the bulb and battery are never shown wired together (no wire or direct contact between them), or the clip is a single static frame with no action at all.
level_2: The bulb and at least one battery share the frame but have no visible electrical connection between them, and/or the second battery never appears, and/or only one battery is ever shown across the whole clip.
level_3: The bulb and two identical batteries are all visible in one fixed shot; the bulb is connected to the first battery through a visible wire or direct metal contact; a second battery is then brought in and connected end-to-end with the first while the bulb stays connected; both batteries are recognizable as the same type and size.
level_4: Everything required for a 3 holds, and additionally: the two batteries match each other in size, shape, and casing color; the bulb's filament is unobstructed and centered in frame; every connection point (battery-to-battery, battery-to-bulb) shows continuous metal contact with no visible gap or insulation covering it; nothing extraneous blocks the view of the circuit.
level_5: Everything required for a 4 holds, and additionally: the bulb stays lit for the entire clip across both the one-battery and two-battery phases with no object entering or leaving frame, no occlusion of the bulb or batteries, and the camera viewpoint stays fixed with no cuts, one continuous take of the whole assembly from start to finish (whether the brightness itself actually changes is judged separately, not here).

Scientific and Causal Correctness rubric:
level_1: The bulb is dark in both phases, or it is lit with one battery but goes dark once the second is added, or it gets dimmer instead of brighter after the second battery connects, or its color shifts to something other than the same warm incandescent glow.
level_2: The bulb is lit in both phases but looks equally bright in each (no visible increase), or it does get brighter but flickers, pulses, or dims partway through the second phase, or the second battery is placed beside the first rather than end-to-end in line yet the bulb still brightens regardless of that wiring error.
level_3: The bulb is lit in both the single-battery and two-battery phases; it is visibly brighter once the second battery joins the loop; the second battery contacts the first end-to-end (positive to negative) rather than side by side; the bulb never goes dark while power is present.
level_4: Everything required for a 3 holds, and additionally: the filament's glow is steady and unbroken in both phases with no intermittent flashing; the terminal-to-terminal contact between the batteries is unambiguous (positive of one touching negative of the other), and the bulb connects to the two remaining free terminals with no reversed polarity.
level_5: Everything required for a 4 holds, and additionally: brightness only ever goes up, never dims back down once the second battery is connected; the filament's shape stays the same with no sagging or melting; the bulb's glass or base shows no scorching or discoloration; there is no spark, smoke, or glowing wire suggesting a short; the jump in brightness happens essentially as soon as the two batteries make full contact, with no noticeable delay.

Spatiotemporal Consistency rubric:
level_1: The bulb or a battery disappears and reappears without anything moving it; the lighting on the scene jumps abruptly for no reason tied to the bulb; the bulb changes position or orientation with no cause; a wire bends or stretches in an unnatural way; a battery flips or spins with no hand or object touching it.
level_2: Motion is jerky rather than continuous (objects seem to jump between poses); the light or shadow on the bulb or batteries shifts suddenly mid-clip without any matching change in a light source; the contact point between the batteries, or between a battery and the bulb, shows a gap that appears and vanishes without anything closing it.
level_3: The bulb, wires, and batteries keep the same size, orientation, and relative placement throughout; the second battery moves toward the first in one smooth, straight line; the two batteries visibly align and settle together on contact; the bulb stays put and fully in view the whole time; ambient lighting on the scene looks the same from start to finish aside from the bulb's own brightness change.
level_4: Everything required for a 3 holds, and additionally: no battery casing dents or compresses, no wire kinks or snaps, no ripple appears on the bulb's glass; nothing jitters, zooms, or pans between frames; there is no frozen frame, skipped motion, or repeated frame.
level_5: Everything required for a 4 holds, and additionally: the second battery's approach ends right at contact with the first with no overshoot or bounce-back; once contact completes, the bulb's brightness change unfolds gradually across several frames rather than jumping in a single frame; every object stays in the same depth plane relative to the camera with no parallax drift; the batteries keep their straight-edged shape and the bulb keeps its rounded shape with no lens warping.