A fuse with a circular cross - sectional radius of ` 0.15 mm` blows at `15 A`. What should be the radius of the cross section of a fuse made of the same material that blows at `30 A`?

Explanation

To solve the problem, we need to use the relationship between the fusing current and the radius of the fuse. The key relationship is that the square of the fusing current (I) is directly proportional to the cube of the radius (R) of the fuse:

\[ I^2 \propto R^3 \]

This can be expressed mathematically as:

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