question_answer

A 800 turn coil of effective area \[0.05\text{ }{{m}^{2}}\]is kept perpendicular to a magnetic field\[5\times {{10}^{5}}T\]. When the plane of the coil is rotated by 90º around any of its coplanar axis in 0.1 s, the emf induced in the coil will be: [NEET 5-5-2019]

A) \[2\times {{10}^{3}}\text{ }V\]            

B) 0.02 V

C) 2 V                              

D) 0.2 V

Correct Answer: B

Solution :

            \[emf=\frac{\Delta \phi }{\Delta t}=\frac{BAN}{\Delta t}\] \[=\frac{(5\times {{10}^{5}})(0.05)(8000)}{0.1}\] \[=\frac{200\times {{10}^{-5}}\times {{10}^{-2}}\times {{10}^{2}}}{{{10}^{-1}}}=0.02\,volt\]