A) \[3.75\times {{10}^{-3}}\]N
B) \[3.75\times {{10}^{-2}}\,N\]
C) \[3.75\times {{10}^{2}}\,N\]
D) \[3.75\times {{10}^{-4}}N\]
Correct Answer: A
Solution :
Induced current in the circuit \[i=\frac{Bvl}{R}\] Magnetic force acting on the wire \[{{F}_{m}}=Bil=B\left( \frac{Bvl}{R} \right)\ l\] \[\Rightarrow {{F}_{m}}=\frac{{{B}^{2}}v{{l}^{2}}}{R}\] External force needed to move the rod with constant velocity \[({{F}_{m}})=\frac{{{B}^{2}}v{{l}^{2}}}{R}=\frac{{{(0.15)}^{2}}\times (2)\times {{(0.5)}^{2}}}{3}\]\[=3.75\times {{10}^{-3}}N\]
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