A uniform metallic wire of resistance 20 ohms is stretched uniformly until its length is doubled without changing its mass or density. What is the new electrical resistance of the stretched wire?

💡 Solution & Explanation

When a wire is stretched to double its length while preserving its total volume, its cross-sectional area decreases by a factor of two, making the new length twice and the new area half of the original. Resistance is directly proportional to length and inversely proportional to cross-sectional area, meaning the resistance multiplies by a factor of four relative to the original value. Therefore, 20 ohms multiplied by 8 yields 160 ohms because length scaling squares the resistance change.