JEE PYQ: Current Electricity Question 12
Question 12 - 2021 (18 Mar 2021 Shift 2)
Two wires of same length and thickness having specific resistances $6,\Omega\text{cm}$ and $3,\Omega\text{cm}$ respectively are connected in parallel. The effective resistivity is $\rho,\Omega\text{cm}$. The value of $\rho$ to the nearest integer, is
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Answer: 4
Solution
In parallel: $R_{\text{net}} = \frac{R_1 R_2}{R_1 + R_2}$. $\frac{\rho l}{2A} = \frac{\rho_1 \frac{l}{A} \cdot \rho_2 \frac{l}{A}}{\rho_1 \frac{l}{A} + \rho_2 \frac{l}{A}}$. $\frac{\rho}{2} = \frac{6 \times 3}{6 + 3} = 2$. $\rho = 4$.
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