# Transient analysis, find and draw the waveform uc(t)

Discussion in 'Homework Help' started by ostn, Jun 6, 2011.

1. ### ostn Thread Starter New Member

Jun 5, 2011
3
0
Hi people, i need to know what steps i should go through to solve the problem i have, please help me with some hints or maybe you know where i could find solved similar problem, it will help me a lot to understand this chapter.

the task: before the instant of time t=0, the key is open, the circuit is in the steady state and no energy is stored in the capacitor. At t=0s the key is switched to the"1" position and then, at t=2s it is switched to the "2" position. Find and draw the waveform uc(t) for -1s<=t<=10s.
given R=1kΩ, E=2V, C=2mF.

Thanks a lot guys!

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Last edited: Jun 6, 2011
2. ### Georacer Moderator

Nov 25, 2009
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1,266
When the switch is turned on pos. 1, the capacitor will start to charge itself from the voltage source. The time constant of that circuit is RC, and at t=2s, the capacitor will have acquired a certain voltage.

When the switch is turned on pos. 2, the source is left out of the circuit and the capacitor will be left free to discharge through the two resistors, with a time constant of 2RC.