Q 11-08-019JEE MainJEE Main 2026 (6 Apr, Shift 1)Easy
The two wires $A$ and $B$ of equal cross-section but of different materials are joined together. The ratio of Young's modulus of wire $A$ and wire $B$ is $20/11$. When the joined wire is kept under certain tension the elongations in the wires $A$ and $B$ are equal. If the length of wire $A$ is $2.2$ m, then the length of wire $B$ is ______ m.
Answer: (C) $1.21$
Concept. Joined wires carry the same tension. With equal areas, $\Delta L = \dfrac{FL}{AY}$ is equal when $\dfrac{L}{Y}$ is equal.
Step 1. Condition. $\dfrac{L_A}{Y_A} = \dfrac{L_B}{Y_B}$.
Step 2. Solve.
$$L_B = L_A\frac{Y_B}{Y_A} = 2.2 \times \frac{11}{20} = 1.21\ \text{m}$$
Answer. $1.21$ m (Option C).
Solution by Sreeraj P, M.Sc Physics
