# 3: Direct Current Circuits


• 3.1: Moving Charge
We begin with some mathematical tools for dealing with moving charge, keeping in mind the observed physical law that charge is neither created nor destroyed.
• 3.2: Resistance and Energy Dissipation
We now discard our assumption from electrostatics that conductors allow totally free (instantaneous) movement of electric charge, and take into account the effects of "electrical friction."
• 3.3: Networks of Batteries and Resistors
We can employ analysis similar to what we used in static circuits to circuits that contain electric current passing through resistors, though it requires a twist to the notion of potential difference used in the static case.
• 3.4: Kirchhoff's Rules
Not every conceivable circuit can be analyzed using the tools of the previous section. Here we learn some tools that can be used in more general cases.
• 3.5: RC Circuits
Up to now, we have only considered the role of capacitors under static circumstances. We now incorporate them into our moving-charge networks.

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