A 10-V battery is connected to an RC circuit (R = 6 Ω and C = 10 μF). Initially, the capacitor is uncharged. What is the final charge on the capacitor (in μC)?

Question

A 10-V battery is connected to an RC circuit (R = 6 Ω and C = 10 μF).  Initially, the capacitor is uncharged.  What is the final charge on the capacitor (in μC)?

jamesj · Answer

Clearly in equilibrium the potential difference of the capacitor is 10 volts.  Now just use the definition of capacitance,
C = Q/V
to calculate Q.

anonymous · Answer

so the final charge would be 100?

rulnick · Answer

Final charge is 100 microcoulombs.  I answered in math for you.  See work there.

anonymous · Answer

could you help with this one? The quantity t1/2=τ ln 2 is called the half-life of an exponential decay, where τ=RC is the time constant in an RC circuit.  The current in a discharging RC circuit drops by half whenever t increases by t1/2.  For a circuit with R=1 kΩ and C=4 μF, if the current is 6 mA at t=4 ms, at what time (in ms) will the current be 3 mA?

radar · Answer

For "practical" matters you may consider the capacitor fully charged after 5 time constants.

radar · Answer

Where the time constant is equal to RC.