Write down the different currents and the amounts of time you are calculating for. If one of those values is a variable you can leave it blank. For example you could have currents at 20, 50 and 100 volts and time in 10, 20 and 30 seconds.
Square the current you are calculating for. In order to square a number, multiply it by itself. For example, 20 squared is 20 x 20 = 400; 50 squared is 50 x 50 = 1,000; and 100 squared is 100 x 100 = 10,000.
Multiply the current squared by the amount of time. The equation looks like this: I^2T. "I" stands for current and "T" stands for time. (Ref 1) Repeat Steps 1-3 with all the different currents and/or times. For example: 20^2x10 = 400 x 10 = 4,000 and 50^2x20= 1,000 x 20 = 20,000. Finally 100^2x30= 10,000 x 30 = 300,000.
Plot the numbers on a graph with one side of the graph representing time and the other representing current. For example you would plot 4,000, 20,000 and 300,000 on the graph. Draw a curve between the plot points to see what the inverse time curve looks like for your calculations.