Exams › JEE Main › Physics

A copper wire of cross-section 0.01 cm² carries a tension of 20 N. Using Young's modulus of copper Y = 1.1 * 10¹¹ N/m² and Poisson's ratio = 0.32, find the decrease in cross-sectional area.

1. 1.164 * 10⁻¹² cm²
2. 1.164 * 10⁻⁶ cm²
3. 1.164 * 10⁻⁶ m²
4. 5.82 * 10⁻⁷ cm²

Correct answer: 1.164 * 10⁻⁶ cm²

Solution

Longitudinal strain = (F/A)/Y; the fractional decrease in area is 2*nu*strain, giving about 1.164 * 10⁻⁶ cm².

Related JEE Main Physics questions

• Select the incorrect statement.
• A steel wire has length l and cross-sectional area A. When a certain load is applied, it elongates by 1 cm. If the same load is now applied to another steel wire made of the same material, having twice the length and half the cross-sectional area, what will be its extension?
• For common metals such as aluminium and copper, which sequence correctly represents the relative magnitudes of the elastic moduli?
• A steel sheet fails under a shear stress of 3.5 × 10⁸ N m⁻². The approximate force required to punch a circular hole of diameter 1 cm through a steel plate 0.3 cm thick is:
• A copper wire of fixed volume V is stretched out to a length l. If a constant force F is applied to this wire and it elongates by Δl, which of the following plots would be a straight line?
• A material has Poisson’s ratio equal to 0.5. When a tensile force is applied to a wire made of this material, its cross-sectional area decreases by 4%. The corresponding percentage increase in its length is:

⚔️ Practice JEE Main Physics free + battle 1v1 →