# Circuit

> A series circuit on a rectangular loop: a battery on the left side, a switch on the top, a bulb on the right and a resistor on the bottom.

Page: https://fframes-kit.pages.dev/docs/physics/circuit/
Cargo feature: `physics` (`fframes-kit = { version = "..", features = ["physics"] }`)

A series circuit on a rectangular loop: a battery on the left side, a switch on the top, a
bulb on the right and a resistor on the bottom. Turn a part off (`switch: false`, ..) and
the wire runs on. The switch closes at `on_at` seconds. Then the current flows as dots out
of the battery's long plate, clockwise, and the bulb glows. A label left empty is not drawn.
Gallery scene: `Circuit`.

Gallery clip of `Circuit`: https://fframes-kit.pages.dev/media/scenes/Circuit-ca64f54b.mp4

```rust
use fframes_kit::prelude::*;

fn figure<'a>(ui: &mut Ui<'a, '_, '_>) -> Svgr<'a> {
    ui.show(Circuit {
        center: (0.0, -0.4),
        width: 8.0,
        height: 4.5,
        on_at: 1.4,
        battery_label: "9 V",
        enter: Some(Create::default().into()),
        ..ui.defaults()
    })
}
```

## API

Components are plain structs. Set the fields you need and fill the rest with `..ui.defaults()`: the defaults below come from the current theme (`theme.` values are fields of `Theme`).

### Circuit

| Field | Type | Default | Description |
| --- | --- | --- | --- |
| `center` | `(f64, f64)` | `(0.0, 0.0)` | The middle of the loop, in units of `ui.space`. |
| `width` | `f64` | `8.0` | Width of the loop in units of `ui.space`. |
| `height` | `f64` | `4.5` | Height of the loop in units of `ui.space`. |
| `battery` | `bool` | `true` | Draws the battery on the left side; off leaves the wire running on. |
| `switch` | `bool` | `true` | Draws the switch on the top side; off leaves the wire running on and the current starts at `on_at`. |
| `bulb` | `bool` | `true` | Draws the bulb on the right side; off leaves the wire running on. |
| `resistor` | `bool` | `true` | Draws the resistor on the bottom side; off leaves the wire running on. |
| `on_at` | `f32` | `1.0` | Seconds after the local start when the switch begins to close and the current starts. |
| `current_speed` | `f32` | `160.0` | Speed of the current dots along the wire, in pixels per second. |
| `dots` | `usize` | `28` | Number of dots that make up the current, spread evenly around the loop. |
| `battery_label` | `&str` | `"9 V"` | Text beside the battery; empty for none. |
| `switch_label` | `&str` | `""` | Text above the switch; empty for none. |
| `bulb_label` | `&str` | `""` | Text beside the bulb; empty for none. |
| `resistor_label` | `&str` | `"R"` | Text below the resistor; empty for none. |
| `wire_color` | `Color` | `theme.colors.text` | Colour of the wire and the parts. |
| `dot_color` | `Color` | `theme.colors.accent` | Colour of the current dots. |
| `glow_color` | `Color` | `theme.colors.highlight` | Colour of the bulb's glow once current flows. |
| `label_color` | `Color` | `theme.colors.text` | Colour of the labels. |
| `stroke_width` | `f32` | `theme.stroke.regular` | Wire width in pixels; the battery's short plate is 2.5 times as thick. |
| `enter` | `Option<EnterAnim>` | `None` | How the wire and the parts draw in; `None` shows them from the start. |
| `exit` | `Option<ExitAnim>` | `None` | How the wire and the parts leave at the end of the container; `None` stays. |
| `parts_enter` | `Option<FadeIn>` | `None` | How the labels, dots and glow fade in; `None` for none. |
| `parts_exit` | `Option<FadeOut>` | `None` | How the labels, dots and glow fade out before the end; `None` for none. |

Methods:

- `fn lever_angle(&self, now: f32) -> f64`: The angle of the switch's lever, from open (35°) to closed (0).
- `fn flowing(&self, now: f32) -> f32`: Seconds the current has flowed at `now` seconds of local time, 0 before it starts.

Feature `physics` · [Source](https://github.com/khanhthanhdev/fframes-kit/blob/main/fframes-kit/src/kits/physics/circuit.rs#L26)