Postprocessing
The Electrical Circuits interface, unlike most of the other physics interfaces, solves for a relatively large number of global dependent variables (such as voltages and currents), instead of solving for a few space-varying fields (such as temperature or displacement). For this reason, the Electrical Circuit interface does not provide default plots when computing a Study.
The physics interface defines a number of variables that can be used in postprocessing. All variables defined by the Electrical Circuit interface are of a global scope and can be evaluated in a Global Evaluation node (under Derived Values). In addition, the time evolution or dependency on a parameter can be plotted in a Global plot (under a 1D Plot Group node).
The physics interface defines a node voltage variable for each electrical node in the circuit, with name cir.v_name, where cir is the physics interface label and <name> is the node’s name. For each two pin component, the physics interface also defines variables containing the voltage across it and the current flowing through it.
In the COMSOL Multiphysics Reference Manual: