Posted by Sandhya on .
A 12 V battery is connected to 5 mega ohm resistor and a 6 micro farad capacitor and an open switch. After how many seconds will the voltage across the resistor reach 9 V?
Suppose the battery is replaced by 12 V ac with a frequency of 60 Hz.Calculate the Irms in the circuit

Physics 
bobpursley,
If the resistor is 9v, the capacitor is 3 volts.
Vc=q/C=12/(5E6*6E6)*e^t/rc
3*30/12=e^t/30
take the ln of each side, solve for t.
check my typing, my eyes are blurry this am.
Now for the ac part, Z=5E6+1/(2PI60)*6E6 figure that, it is nearly all resistive.
Then I=12/Z
I can check your work on this.