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 Name. For each two-pin component, the physics interface also defines variables containing the voltage across it and the current flowing through it. For resistors it adds a heat source variable as well.
In the COMSOL Multiphysics Reference Manual: