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Question: There is a current of 20 amperes in a copper wire of \(10 ^ { - 6 }\) square metre area of cross-s...

There is a current of 20 amperes in a copper wire of 10−610 ^ { - 6 } square metre area of cross-section. If the number of free electrons per cubic metre is 102910 ^ { 29 }, then the drift velocity is.

A

125×10−3 m/sec125 \times 10 ^ { - 3 } \mathrm {~m} / \mathrm { sec }

B

12.5×10−3 m/sec12.5 \times 10 ^ { - 3 } \mathrm {~m} / \mathrm { sec }

C

1.25×10−3 m/sec1.25 \times 10 ^ { - 3 } \mathrm {~m} / \mathrm { sec }

D

1.25×10−4 m/sec1.25 \times 10 ^ { - 4 } \mathrm {~m} / \mathrm { sec }

Answer

1.25×10−3 m/sec1.25 \times 10 ^ { - 3 } \mathrm {~m} / \mathrm { sec }

Explanation

Solution

vd=inAe=201029×10−6×1.6×10−19v _ { d } = \frac { i } { n A e } = \frac { 20 } { 10 ^ { 29 } \times 10 ^ { - 6 } \times 1.6 \times 10 ^ { - 19 } } =1.25×10−3 m/s= 1.25 \times 10 ^ { - 3 } \mathrm {~m} / \mathrm { s }