question_answer

A particle of mass 0.6 g and having charge of 25 nC is moving horizontally with a uniform velocity \[\text{1}\text{.2}\times \text{1}{{\text{0}}^{\text{4}}}m{{s}^{-1}}\] in a uniform magnetic field, then the value of the magnetic induction is \[(g=10\,m{{s}^{-2}})\]                                                      [EAMCET 2001]

A)            Zero                                         

B)            10 T

C)            20 T                                          

D)            200 T

Correct Answer: C

Solution :

                   Particle will move with uniform velocity when it?s acceleration is zero.                 i.e. \[|{{F}_{m}}|\,=\,mg\Rightarrow mg=qvB\] \[\Rightarrow B=\frac{mg}{qv}=\frac{0.6\times {{10}^{-3}}\times 10}{25\times {{10}^{-9}}\times 1.2\times {{10}^{4}}}=20\,T\]