A circular plastic disk with radius R = 2.00 cm has a uniformly distributed charge `Q = + (2.00 xx 10^(6))e` on one face. A circular ring of width `40 mu m` is centers on that face, with the center of that width at radius r = 0.50 cm. In coulombs, what charge is contained within the width of the ring ?

Explanation

To find the charge contained within the width of the ring centered on the face of the circular disk, we can follow these steps:

### Step 1: Determine the Surface Charge Density (σ)
The surface charge density (σ) can be calculated using the formula:

\[ \sigma = \frac{Q}{A} \]
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