Without the circuit, it is hard to tell.
It could be as simple as the RC time constant
RC=40E-6 seconds, you know R, calculate C
In the figure , the total resistance is 13.0 k \Omega, and the battery's emf is 32.0 V. If the time constant is measured to be 40.0 \mu s. Calculate the total capacitance of the circuit.
2 answers
There is no figure. Have you noticed that?
In an RC circuit, the time constant is RC.
Solve for C
In an RC circuit, the time constant is RC.
Solve for C