# Homework Help: Series circuit problem - am I correct?

1. Nov 18, 2008

### bcjochim07

1. The problem statement, all variables and given/known data
A simple series circuit consists of a 150 ohm resistor, a 25 V battery, a switch and 2.5 pF parallel plate capacitor(uncharged initially) w/ plates 5mm apart. The switch is closed at t=0.

What is the maximum electric flux and maximum displacement current through the capacitor?

2. Relevant equations

3. The attempt at a solution
Maximum flux will be achieved when the capacitor is fully charged, at
Vc = Vbat Vc = 25 V Q = (2.5*10^-12)(25) = 6.25 * 10 ^-11 C
Electric flux = EA cos(theta)= qin/epsilon
6.25*10e-11 / 8.85e-12 = <b> 7.06 Vm^2 </b>

Displacement current = 8.85* 10e-12 * dFluxElectric/dt

which = I/epsilon

I need to find the Imax, so I used the formula for the charging of a capacitor:

Q = Qmax(1-e^-t/RC)
I = -dQ/dt = -Qmax/RC * (1-e^-t/RC) RC = 3.75 e-10

the maximum I is Qmax/RC Qmax is calculated above to be 6.25e-11
so Imax is .167 A

so I think the maximum displacement current is .167 A

Did I do this right?