step response of a RC circuit asking for i(t)

[danielerbe]

1. The problem statement, all variables and given/known data
In attachment


2. Relevant equations
i dont understand why it would be asking for the current going through the capcitor, in a dc circuit it should be an open circuit but there will be a voltage over it... after searching through lecture notes and text book cant find anything relating to I(t) in a RC DC circuit.
could anyone point me in the direction of a recourse that will explain this to me or give me some idea about what the qestion is asking?... thanks in advance.

[Andrew Mason]

1. The problem statement, all variables and given/known data
In attachment


2. Relevant equations
i dont understand why it would be asking for the current going through the capcitor, in a dc circuit it should be an open circuit but there will be a voltage over it... after searching through lecture notes and text book cant find anything relating to I(t) in a RC DC circuit.
could anyone point me in the direction of a recourse that will explain this to me or give me some idea about what the qestion is asking?... thanks in advance.
When the applied voltage changes, there is a brief current that depends on the value of R and C. What is the charge in the capacitor with the 30 V battery connected? What happens to the charge when that battery is removed and the 12V battery is connected? Since there is a change in charge what is dQ/dt?

AM