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See the circuit at: https://www.circuitlab.com/circuit/8avg9d/pp-6_3/ Current across the 100uF capacitor is i(t) = 50 sin (120 pi t) mA the text book says take v(0) = 0, though I suspect they mean i(0) = 0 Find voltage across capacitor at t = 1 ms and t = 5 ms I'm getting different answers by hand, from the text, and what I'm getting in circuit lab... thus far, CL has been correct in all cases.. though the text and myself make plenty of errors.

Do I have the problem setup in CL correctly?

ah, yes, it is v(0) = 0... but still not clear if I have the remaining setup correctly.

ok, I by hand, I now get the text book answer, which differs from circuit lab.
at t=1ms, 93.114 mV; t=5ms, 1.735 mV. what do i have wrong in CL?

@DYLH,

Um.

Time for a sanity check.

If, at T=0, the capacitor voltage starts at 0V and the current starts at 0mA then over the whole of the 5ms period of the problem, the current into the capacitor is positive; i.e. it is flowing into the cap and so the voltage across it is increasing positively from zero.

Therefore the voltage across the cap cannot be less at 5ms than it is at 1ms!

oops, yes, the units on t=5ms should be V, not mV. Anyway, these are the values I get by hand and in the book.. but not what I'm getting in CL. can you address my actual question?

Your time step is too big.

CL suggests:

https://www.circuitlab.com/docs/the-basics/#time_domain_simulation

but in many cases - of which yours is one - a time step of at least

(Stop Time-Start Time)/1000

will be more appropriate:

https://www.circuitlab.com/circuit/d4qjc5/relaxation-osc-fixed-01/

:)