JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 26 August 2021, Shift 1, Physics Q17

Question 17 of 90 in this shift, Physics question 17 of 30, Section A.

What equal length of an iron wire and a copper-nickel alloy wire, each of 2 mm diameter connected parallel to give an equivalent resistance of 3

\Omega

? (Given resistivities of iron and copper-nickel alloy wire are 12

\mu\Omega

cm and 51

\mu\Omega

cm respectively)

(1)110 m
(2)97 mOfficial answer
(3)90 m
(4)82 m

Official answer

Option 2

NTA final key.

Chapter: Current Electricity
Topic: Ohm's Law and Resistance
Idea tested: Resistivity and Geometry

Same idea in other shifts

Asked 10× in all

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.