- #1

Dilemma

- 15

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1. Homework Statement

1. Homework Statement

Assuming that the dielectric is inserted at a constant rate, find the current I as the slab is inserted.

Express your answer in terms of any or all of the given variables V, K, r, d, Δt, and ε0, the permittivity of free space.

## Homework Equations

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C = ε0 * A / d

## The Attempt at a Solution

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Q = CV

dQ = dC ⋅ V

I = dQ/Δt

C = ∈ ⋅ A / d = ∈⋅(xr)K / d + ∈⋅(r-x)r / d

dC = ∈⋅(r)K / d - ∈⋅r / d = ∈r(K-1)/d

dQ = dC⋅V

Therefore answer should be ∈r(K-1)V/(dΔt)

However, the correct answer is ∈(r^2)(K-1)V/(dΔt). That means the multiplier "r" is missing. What is wrong with my solution.

Thanks in advance.