JEE Main 2022 · 29 Jul · Shift 1 · Physics Q42

← JEE Main 2022 · 29 Jul · Shift 1

PhysicsSingle correct+4 / -1Question 42 of 90

Two metallic wires of identical dimensions are connected in series. If $\sigma_1$ and $\sigma_2$ are the conductivities of the these wires respectively, the effective conductivity of the combination is :

\dfrac{\sigma_1\sigma_2}{\sigma_1+\sigma_2}

\dfrac{2\sigma_1\sigma_2}{\sigma_1+\sigma_2}

\dfrac{\sigma_1+\sigma_2}{2\sigma_1\sigma_2}

\dfrac{\sigma_1+\sigma_2}{\sigma_1\sigma_2}

Answer and worked solution

Official answer: B

Series. $\dfrac{2L}{\sigma A}=\dfrac L{\sigma_1A}+\dfrac L{\sigma_2A}$ , so $\sigma=\dfrac{2\sigma_1\sigma_2}{\sigma_1+\sigma_2}$ .

(B)

Topics:Ohm's law and resistivity Series and parallel resistors

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JEE Main 2022 · 29 Jul · Shift 1, Physics question 42