If a copper wire is stretched to make its radius decrease by `0.1%`, then the percentage increase in resistance is approximately -

Explanation

To solve the problem of finding the percentage increase in resistance when the radius of a copper wire is decreased by 0.1%, we can follow these steps:

### Step 1: Understand the relationship between resistance and dimensions of the wire
The resistance \( R \) of a wire is given by the formula:
\[ R = \rho \frac{L}{A} \]
where:
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