Adding components
=================

A resistor
----------

Circuits are, at their core, made of components, and our current shunt is no different.
Let's start with adding just one resistor. To do this, we'll use the :class:`~.Resistor`
mobject.

.. code-block:: python

    class CurrentShunt(Scene):
        def construct(self) -> None:
            r = Resistor()

            self.add(r)

This gets us the visual below. If you're confused as to why it's a box and not a
squiggle, it's because I'm European, and therefore use (mostly) European circuit
symbols.

.. manim:: CurrentShunt
    :save_last_frame:
    :hide_source:

    from manim_eng import *
    config_eng.debug = False

    class CurrentShunt(Scene):
        def construct(self) -> None:
            r = Resistor()

            self.add(r)

In our target circuit, the resistor is vertical, so let's quickly fix that.

.. code-block:: python

    class CurrentShunt(Scene):
        def construct(self) -> None:
            r = Resistor().rotate(90 * DEGREES)

            self.add(r)

.. manim:: CurrentShunt
    :save_last_frame:
    :hide_source:

    from manim_eng import *
    config_eng.debug = False

    class CurrentShunt(Scene):
        def construct(self) -> None:
            r = Resistor().rotate(90 * DEGREES)

            self.add(r)

Much better!

The current source and other resistor
-------------------------------------

To add a current source we'll use the aptly named :class:`~.CurrentSource` mobject. We'll
also add in the second resistor.

.. code-block:: python

    class CurrentShunt(Scene):
        def construct(self):
    r1 = Resistor().rotate(90 * DEGREES)
    r2 = Resistor().rotate(90 * DEGREES).shift(2 * RIGHT)
    isource = CurrentSource().rotate(90 * DEGREES).shift(2 * LEFT)

    self.add(r1, r2, isource)

.. manim:: CurrentShunt
    :save_last_frame:
    :hide_source:

    from manim_eng import *
    config_eng.debug = False

    class CurrentShunt(Scene):
        def construct(self):
            r1 = Resistor().rotate(90 * DEGREES)
            r2 = Resistor().rotate(90 * DEGREES).shift(2 * RIGHT)
            isource = CurrentSource().rotate(90 * DEGREES).shift(2 * LEFT)

            self.add(r1, r2, isource)

Note that the current source is again the European symbol.

Adding component labels
-----------------------

Let's add some labels to our components. This is done using the
:meth:`~.Component.set_label` method for the resistors, and
:meth:`~.Component.set_current` to specify the current through the current source.

.. code-block:: python

    class CurrentShunt(Scene):
        def construct(self):
            r1 = Resistor().rotate(90 * DEGREES)
            r2 = Resistor().rotate(90 * DEGREES).shift(2 * RIGHT)
            isource = CurrentSource().rotate(90 * DEGREES).shift(2 * LEFT)

            r1.set_label("R_1")
            r2.set_label("R_2")
            isource.set_current("I_0")

            self.add(r1, r2, isource)

.. manim:: CurrentShunt
    :save_last_frame:
    :hide_source:

    from manim_eng import *
    config_eng.debug = False

    class CurrentShunt(Scene):
        def construct(self):
            r1 = Resistor().rotate(90 * DEGREES)
            r2 = Resistor().rotate(90 * DEGREES).shift(2 * RIGHT)
            isource = CurrentSource().rotate(90 * DEGREES).shift(2 * LEFT)

            r1.set_label("R_1")
            r2.set_label("R_2")
            isource.set_current("I_0")

            self.add(r1, r2, isource)

.. note::

    We could have used :meth:`~Component.set_label` on the current source as well, but
    then we wouldn't know which direction the current was flowing in.

Well this doesn't look bad, but we're missing the other important part of a circuit ---
the wires. Read on!