A current of 10 A exists in a wire of crosssectional area of 5 mm$^2$ with a drift velocity of $2\times10^{-3}$ ms$^{-1}$. The number of free electrons in each cubic meter of the wire is __________.

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 17 March 2021, Shift 1, Physics Q5

Question 5 of 90 in this shift, Physics question 5 of 30, Section A.

A current of 10 A exists in a wire of crosssectional area of 5 mm

^2

with a drift velocity of

2\times10^{-3}

^{-1}

. The number of free electrons in each cubic meter of the wire is __________.

(1) $2\times10^{6}$
(2) $1\times10^{23}$
(3) $625\times10^{25}$ Official answer
(4) $2\times10^{25}$

Official answer

Option 3

NTA final key.

Chapter: Current Electricity
Topic: Ohm's Law and Resistance
Idea tested: Drift Velocity and Current

Same idea in other shifts

Asked 5× 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.