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38 2. Tutorial
{V0, {1, 2}, V0}
Hence, a positive value for the branch current, I$V0 , denotes a current flowing from node 1 to
node 2. So whenever a circuit analysis yields a negative result for I$V0 there is nothing wrong. This
just means that the current is in fact flowing into the opposite direction, i.e. from node 2 to node 1.
Element Values
As opposed to SPICE, the values of circuit elements need not be purely numerical quantities. Since
Mathematica is capable of performing mathematical calculations symbolically, the element values may
also be any symbolic or mixed symbolic/numeric expressions. In the voltage-divider example (see
Figure 2.1) we assigned a numerical value of 10 (Volts) to the voltage source whereas we used the
symbolic values R1 and R2 for the two resistors. (Note that you don’t have to specify any units
like Volts for numerical values.) In this case, the symbols used for the values of the resistors are
identical to the reference designators, but we could also have supplied any other valid Mathematica
expression.
1
R1=R
V0
out
R2=2*R
Figure 2.4: Voltage divider circuit with different node names and resistor values
Let’s make use of some of the facts presented in the preceding paragraphs by renaming node 2 of
the voltage divider to out, arbitrarily making the assignments R1 ⩵ R and R2 ⩵ R, and rewriting
the netlist accordingly (see Figure 2.4):
In[4]:= voltageDivider2 =
Netlist[
{V0, {1, 0}, 10},
{R1, {1, out}, R},
{R2, {out, 0}, 2 R}
]
Out[4]= NetlistRaw, 3