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There is a current of $20$ amperes in a copper wire of ${10^{ - 6}}$ square meter area of cross-section. If the number of free electrons per cubic meter is ${10^{29}}$, then the drift velocity is
  • A$125 \times {10^{ - 3}} \,m/sec$
  • B$12.5 \times {10^{ - 3}} \,m/sec$
  • C$1.25 \times {10^{ - 3}} \,m/sec$
  • D$1.25 \times {10^{ - 4}} \,m/sec$
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