question_answer

There is a current of 20 amperes in a copper wire of \[{{10}^{-6}}\] square metre area of cross-section. If the number of free electrons per cubic metre 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)            \[1.25\times {{10}^{-4}}m/sec\]