question_answer

A 10 m long copper wire while remaining in the east-west horizontal direction is falling down with a speed of 5.0 m/s. If the horizontal component of the earths magnetic field \[=0.3\times {{10}^{-4}}Wb/{{m}^{2}}\]the emf developed between the ends of the wires is

A)  0.15 V                                  

B)  1.5 V

C)  0.15 mV              

D)         1.5 mV

Correct Answer: D

Solution :

Given,\[l=10\,\,m,\,\,v=5\,\,m/s\] and        \[H=0.3\times {{10}^{-4}}\,\,Wb/{{m}^{2}}\] Induced\[emf\,\,e=Hvl\]                 \[=0.3\times {{10}^{-4}}\times 5\times 10\]                 \[=1.5\times {{10}^{-3}}\,\,V\]                 \[=1.5\,\,m\,\,V\]