There is never any current THROUGH a capacitor. The correct answer to both questions is choice (A), zero amps. However, I'm not sure that was what the quiz-constructor meant: he/she may be a moron.

7. (D)

I of C = C dV/dt = (.000010F)*(10V/.002s) = .05 Amps = 50 mA

8. (A)

I of C = C dV/dt = (.000010F)*(0V/4s) = 0 Amps

Note: I of C goes to 0 Amps immediately when the Voltage across C quits changing. I of C not = C dV/dt + (existing current). I of C only = C dV/dt

q = CV

Thus is is possible to rescale the voltage axis as charge (on the capacitor) by multiplying by C.

q = it

. . .

i = dq/dt

Thus each section with a constant slope has a particular dq/dt, where the slope is the current.

I=C dV/dt + Io at all times, where Io is the current when the slope of the voltage changes.

Not sure how to approach this question ?