Question

Capacitors won't hold a charge indefinitely; as time goes on, charge gradually migrates from the positive to the negative plate. We can model this as a discharge of the capacitor through an internal "leakage resistance." A 0.49F capacitor charged to 3.7V will initially discharge with a leakage current of 0.25mA .

I found the leakage resistance to be 1.5

Answer 1

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Capacitors won't hold a charge indefinitely; as time goes on, charge gradually migrates from the positive to the negative plate. We can model this as a discharge of the capacitor through an internal "leakage resistance." A 0.34F capacitor charged to 3.3V will initially discharge with a leakage current of 0.40mA

How long will it take for the capacitor voltage to drop to 1.0?

answer

   Resistance of the dielectric material

   R   =   Initial votlage / initial current

         =   3.3 / 0.40 * 10^-3   

         =   8.25 * 10³   ?

   voltage across a capacitor duting discharge is given by

   V   =   V₀ * e^-t/RC

   1.0   =   3.3 * e^-t/RC

   =>   e^t/RC    =   3.3 / 1.0

   Taking natural log on both sides

   t/R * C   =   ln (3.3)

   t   =   8.25 * 10³ * 0.35 * ln (3.3)

=   3.35 * 10³   s