Find Dielectric Constant Given Charges

[Runaway]

Homework Statement

When a certain air-filled parallel-plate capacitor is connected cross a battery, it acquires a charge (on each plate) of 130 μC. While the battery connection is maintained, a dielectric slab is inserted into and fills the region between the plates. This results in the accumulation of an additional charge of 190 μC on each plate.
What is the dielectric constant of the dielectric slab?

Homework Equations

k = E₀/E

The Attempt at a Solution

I have no idea, any guidance as to where to start would be great.

 

[ideasrule]

What's the equation for the capacitance of a parallel-plate capacitor? How does this depend on the dielectric constant?

 

[Runaway]

C= k\epsilon₀ A / d
so k= C/ (\epsilon₀ A / d)
But I still don't have A or d, so how does that help me?

 

[ideasrule]

C= k\epsilon₀ A / d
so k= C/ (\epsilon₀ A / d)

It should be \epsilon, not \epsilon₀, if a dielectric is present. The dielectric constant is just k=\epsilon/\epsilon₀.

But I still don't have A or d, so how does that help me?

Well, you know that Q=CV for both situations: with the dielectric and without. You also know that V is a constant.

 

[Runaway]

ok, so k = q/q₀