JEE Mains · Physics · STD 12 - 3. current electricity
A current of \(10\, A\) exists in a wire of crosssectional area of \(5\, mm ^{2}\) with a drift velocity of \(2 \times 10^{-3}\, ms ^{-1}\). The number of free electrons in each cubic meter of the wire is ..........
- A \(2 \times 10^{6}\)
- B \(625 \times 10^{25}\)
- C \(2 \times 10^{25}\)
- D \(1 \times 10^{23}\)
Answer & Solution
Correct Answer
(B) \(625 \times 10^{25}\)
Step-by-step Solution
Detailed explanation
\(i =10 A , A =5 mm ^{2}=5 \times 10^{-6} m ^{2}\) and \(v _{ d }=2 \times 10^{-3} m / s\) We know, \(i= neAvd\) \(\therefore 10= n \times 1.6 \times 10^{-19} \times 5 \times 10^{-6} \times 2 \times 10^{-3}\) \(\Rightarrow n =0.625 \times 10^{28}=625 \times 10^{25}\)
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