2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Magnetism

JEE Main & Advanced Physics Magnetism Question Bank Self Evaluation Test - Magnetism and Matter

  • question_answer
    The coercivity of a small magnet where the ferromagnet gets demagnetized is\[3\times {{10}^{3}}\,A{{m}^{-1}}\]. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is:             

    A) 30 mA 

    B) 60 mA

    C) 3 A  

    D) 6 A

    Correct Answer: C

    Solution :

    [c] Magnetic field in solenoid \[B={{\mu }_{0}}ni\] \[\Rightarrow \,\,\,\,\frac{B}{{{\mu }_{0}}}=ni\]   (Where n = number of turns per unit length) \[\Rightarrow \,\,\,\,\frac{B}{{{\mu }_{0}}}=\frac{Ni}{L}\Rightarrow 3\times {{10}^{3}}=\frac{100i}{10\times {{10}^{-2}}}\] \[\Rightarrow \,\,\,i=3A\]


You need to login to perform this action.
You will be redirected in 3 sec spinner