Counter-Strike: Source Easter Egg - Physics Equation

I was playing CS Source today when i noticed some interesting graffiti. It is on the level CS Assault on a wall down the side alley, (the alley outside of the building with the metal stairs leading up to the upper floor entrance). The graffiti basically depicts a crude drawing on an electric circuit which contains what seems to be a resistor and an AC power supply. It also has V, I and R written on it in that order, (screenshot below).
For all you physics buffs, i am sure you will recognise this as being the equation 'Voltage = Current x Resistance'. I personally think this is fairly intresting as in HL2 Episode 1, an equation for Resistivity was found on a wall (see http://www.eeggs.com/items/50434.html) which i also submitted to eeggs.com; valve in my opinion, by including physics equations in their games seem to be referencing the fact that their source games were really the first to look at the physics and dynamics behind previously inanimate objects.
Even though i stated that the circuit seems to include a resistor and an AC power supply, i cannot be completely sure as the power supply has two arrows next to it and the resistor has an arrow above it. If anyone knows any better than me and can correct this, please feel free.