I am finding the value of the time constant in a circuit from the graph and by the CR equation. When using the graph I am getting t= 50s and when using the equation t=CR the answer is 2.09. Can someone help me please?

Answer 1

I assume you are talking about some transient situation like the discharge of a capacitor in an RC circuit, for which
I = Io e^(-t/RC)

If RC = 2.09s, your graph should show that I/Io = 1/e = 0.3679 at t = 2.09 s

Without seeing your graph and how you did the analysis, I cannot pinpoint the cause of your problem