The applet calculates the transmembrane potential in the presence of multiple ion species using the Goldman-Hodgkin-Katz Equation. The concentrations of potassium, sodium, and chloride ions inside and outside the cell as well as their permeabilities can be varied to observe the effects on the membrane potential. The yellow line indicates the membrane separating the intracellular medium (In) from the extracellular medium (Out). The value of the membrane potential as well as the Nernst potential for the respective ions is plotted in the graph.