Physics
posted by ALan on .
A 3.00 uF and a 5.00 uF capacitor are connected in series cross a 30.0V battery. A 7.00 uF capacitor is then connected in parallel across the 3.00 uF capacitor.
a)Calculate the equivalent capacitance of the circuit
I think the answer is 3.33 uF.
b)Determine the voltage across the 7.00 uF capacitor.
Im not sure how to do this one. Help please?
Thanks

a) correct
b) 10microC in parallel with 5microfarad.
Same q on each, C=Q/V.
Total capacitance= 3.33micro, Q then equals 3.33micro*30v= 99.9E6 coulombs
So, in the 5micro, then V=q/C=99.9E6/5E6=19.99volts
So the remainder voltage is across the 7uf is 10 volts. 
Thanks

ulol tanga!