Domain: Engineering — Electrical Engineering
Target concept: Smoothing of flickering LEDs driven by fast-switching signals using an RC low-pass filter

Video generation prompt: On the desk, a battery-powered square wave source drives two identical LEDs placed side by side: one LED is wired directly across the source's output, while the other LED is wired in parallel with a capacitor, and this LED–capacitor pair is connected to the source through a series resistor, with the capacitor's other terminal tied to ground.

Evaluation guide:
(i) Target concept: Low-pass filtering of digital switching signals via RC integration to suppress perceptible LED flicker.
Minimum mechanism: Capacitor must charge/dissipate through resistor during square wave transitions, producing exponential voltage rise/fall across LED, preventing full discharge (extinction) within off-phase duration.
(ii)Storyline: Frame 0–2: Static wide shot showing desk, square wave source, and two side-by-side LEDs in idle (off) state. Frame 3–4: Source activates: direct LED instantly turns on, then sharply cuts off; RC LED begins gradual brightening. Frame 5–8: Direct LED sustains discrete on/off cycling with dark gaps; RC LED reaches stable brightness and remains continuously illuminated with smooth analog-like variation, no zero-crossing. Frame 9–10: Final stable contrast held, both LEDs visible, side-by-side, with unambiguous flicker vs. non-flicker states. Viewpoint: Fixed frontal desk-level angle; no zoom/pan; all components fully in-frame and unoccluded.

Manual:
Experimental Procedure
1. Place battery-powered square wave source on desk.
2. Mount two identical LEDs side-by-side on desk.
3. Connect first LED directly to source output.
4. Connect second LED in parallel with a capacitor; connect this LED-capacitor pair to the same source output through a series resistor; connect the capacitor's other terminal to ground.
Observation of Experimental Phenomena
The directly driven LED flickers rapidly with visible on/off gaps; the RC-driven LED emits steady, continuous light with no perceptible flicker or extinction.
Summary of Experimental Principles
An RC low-pass filter smooths fast-switching square wave signals by integrating current through the capacitor, reducing high-frequency harmonics and eliminating visible flicker in LEDs.

Prompt Grounding rubric:
level_1: No battery-powered square wave source is visible; one or both LEDs are missing, or the two LEDs are shown far apart or stacked instead of positioned next to each other; no resistor-capacitor network is shown; no ground connection is visible; the desk surface or lab setting is absent.
level_2: At least one LED and the desk setting are visible, but two or more of the following are missing: the square wave source, the second LED, the two LEDs positioned next to each other, the resistor-capacitor network, the ground connection, or the direct wire to the first LED.
level_3: The battery-powered square wave source, two identical LEDs next to each other, and the desk surface are all present; one LED has a plain direct wire to the source; the other LED sits alongside a resistor and a capacitor, but the capacitor's connection to ground is not clearly shown (e.g., no visible ground symbol or wire).
level_4: The square wave source, the two LEDs positioned next to each other, and the desk are all present and correctly wired: the first LED connects directly to the source with no components in between; the second LED is wired in parallel with a capacitor, with a resistor in series between the source and this LED-capacitor pair, and the capacitor's far terminal is clearly connected to a visible ground point or symbol; nothing extraneous blocks the view of the setup.
level_5: The two LEDs match each other in size, shape, and color; the square wave source is clearly identifiable as battery-powered (e.g., a visible battery symbol or casing) and as producing a repeating square wave (e.g., a labeled waveform or blinking indicator); the resistor-capacitor branch shows a single unambiguous path with no stray or duplicate components; the ground connection is one continuous, clearly traceable wire from the capacitor to the ground point; the correct wiring from the 4-score level is also present.

Scientific and Causal Correctness rubric:
level_1: Neither LED shows any change in brightness over time (both stay constantly lit or constantly dark), so there is no way to compare flicker behavior between the direct-driven LED and the RC-filtered LED.
level_2: Only one of the two LEDs shows any brightness change over time; the other stays constantly on or constantly off; there is no visible contrast between how the two LEDs respond to the square wave, so the filtering effect of the resistor-capacitor network cannot be seen.
level_3: Both LEDs show changing brightness over time, and the directly driven LED clearly switches on and off with visible dark gaps, while the RC-filtered LED looks noticeably steadier with less pronounced on/off gaps; however this contrast is not consistent for the whole clip: at some points the RC-filtered LED flickers about as much as the direct one, or the pattern briefly reverses.
level_4: The directly driven LED shows rapid, sharp on/off switching with visible dark gaps between pulses; the RC-filtered LED, by contrast, stays visibly lit without dropping to darkness, its brightness easing up and down smoothly rather than switching abruptly; this steady contrast between the two LEDs holds for the entire clip, matching what an RC low-pass filter should do to a fast square wave.
level_5: The direct-driven LED's on/off pattern tracks the square wave's timing closely, with crisp transitions and roughly equal bright/dark durations; the RC-filtered LED's brightness rises and falls smoothly with no sudden jumps, no overshoot beyond a stable brightness, and never dips to full darkness at any point in the clip, showing the RC network fully smoothing out the switching signal.

Spatiotemporal Consistency rubric:
level_1: The LEDs or resistor-capacitor components appear to jump to new positions between frames with no motion connecting them; components vanish or appear suddenly; the desk surface or background changes abruptly; the lighting on the scene shifts with no visible cause.
level_2: One of the LEDs visibly drifts out of its original spot over the course of the video even though nothing appears to be moving it; a wire or component appears disconnected in one frame and reconnected in the next with no visible hand or motion causing it; the direction of shadows on the desk shifts partway through the clip even though the viewpoint stays fixed.
level_3: The LEDs and the resistor-capacitor components hold their positions and orientation well enough that a viewer would not suspect any drift, though very close inspection might catch faint unevenness in their outlines from frame to frame; lighting stays close to constant and is not obviously tied to which LED is lit; the resistor-capacitor branch keeps the same series arrangement throughout.
level_4: The two LEDs stay rigidly next to each other with the same spacing for the whole clip; the resistor-capacitor components keep the same positions and orientation relative to each other and to the LEDs; there is no visible warping, drifting, or lighting change tied to the LEDs turning on or off; if a hand briefly enters the shot, it moves smoothly and does not cause any component to shift out of place.
level_5: Across the entire clip, the outlines of the LEDs, wires, and resistor-capacitor components stay visually identical in position and shape; shadows and reflections on the desk stay consistent with one fixed light source and one fixed camera viewpoint throughout; any motion in the scene (such as a hand entering or leaving) looks smooth and natural, with no strobing, doubling, or sudden distortion of any component.