A) \[N/m\]
B) \[7\times {{10}^{3}}\,N/m\]
C) \[7\times {{10}^{2}}\,N/m\]
D) \[7\times {{10}^{-2}}\,N/m\]
Correct Answer: C
Solution :
If the area of cross-section of wire is \[1\,\mu m\]and the number of free electrons per unit volume is \[0.3\,\mu m\], the in \[3\,\mu m\] seconds \[3\,\,s\] electrons will pass it. The electric current is given by \[4\,\,s\] \[5\,\,s\] \[6\,\,s\] Where \[\overset{\to }{\mathop{a}}\,\] is the drift velocity of the electrons. Given, \[\overset{\to }{\mathop{b}}\,\] \[\left( \overset{\to }{\mathop{a}}\,+\overset{\to }{\mathop{b}}\, \right)\times \left( \overset{\to }{\mathop{a}}\,-\overset{\to }{\mathop{b}}\, \right)\] \[2\left( \overset{\to }{\mathop{b}}\,\times \overset{\to }{\mathop{a}}\, \right)\] \[-2\left( \overset{\to }{\mathop{b}}\,\times \overset{\to }{\mathop{a}}\, \right)\] Note: Direction of drift velocity is opposite to direction of electric field.You need to login to perform this action.
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