Q. 7

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Found in: Page 652

### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

# The irregularly shaped area of charge in FIGURE has surface charge density. Each dimension (x and y) of the area is reduced by a factor of . a. What is the ratio , where is the final surface charge density? b. An electron is very far from the area. What is the ratio of the electric force on the electron after the area is reduced to the force before the area was reduced?

(a) The ratio of final to initial surface charge density when dimensions (x and y) are reduced by a factor of

(b) The ratio of the electric force on the electron which is very far from the area after the area of positive charge is reduced to the force before the area was reduced is one.

See the step by step solution

## Step 3: Given information (part b)

An electron is very far from the area.

## Step 4: Explanation (part b)

Here, the total charge is constant before and after the shrinkage of the area.

Further, as per the given data, the electron is very far from the area and hence it may be taken not only as a point charge. Thus, the force on the electron by the area of positive charge remains constant before and after its shrinkage as the farthest electron shows no impact on the area.