physics need help
posted by paul on .
A parallelplate capacitor made of circular plates of radius 55 cm separated by 0.25 cm is charged to a potential difference of 1000 Volts by a battery. Then a sheet of tantalum pentoxide is pushed between the plates, completely filling the gap between them. How much additional charge flows from the battery to one of the plates when the tantalum pentoxide is inserted?
where do i find the k for tantalum pentoxide?

for that material, k=25

i tried that for the value of k of that material but i'm still not getting the right answer

I will be happy to critique your work.

C=(kAe)/d
=[(25)(pi*.55^2)(8.85e12)]/.0025
=8.41e8
q1=CV
=(8.41e8)(1000)
=8.41e5
without dielectric:
C=(Ae)/d
=(pi*.55^2)(8.85e12)/.0025
=3.36e9
q2=CV
=(3.36e9) (1000)
= 3.36e6
q1q2
=8.07e5 C 
this is not the right answer though. am i missing a step?

With k=25,all your math is right.

thanks, i finally got the right answer, i just needed to put more digits with the scientific notation.
thanks bob