# Homework Help: Magnetic Field Inside a Charging Capacitor

1. Oct 20, 2013

### Plasmosis1

1. The problem statement, all variables and given/known data
A 10-cm-diameter parallel-plate capacitor has a 1.0 mm spacing. The electric field between the plates is increasing at the rate 1.4×106V/m*s.
What is the magnetic field strength 2.7cm from the axis?

2. Relevant equations

$\oint$B*ds=$\mu$$\epsilon$dE(t)/dt*A
B=($\mu$$\epsilon$dE(t)/dt*A)/(2$\pi$r)

B=($\mu$Id)/(2$\pi$R2)*r
3. The attempt at a solution
I tried using the first equation:
8.85E-12*4$\pi$E-7*1.4E6*$\pi$(0.05)2/(2$\pi$*0.027)=
7.2E-13T which is wrong

2. Oct 20, 2013

### Staff: Mentor

"A" should be the area your integral encloses, not the total area of the capacitor.