JEE Main2014PhysicsMagnetic Properties of MatterActual
The coercivity of a small magnet, where the ferromagnet gets demagnetised is 3 × 10 3 A / m . The current required to be passed in a solenoid of length 10 cm and number of turns 100 , so that the magnet gets demagnetised when inside the solenoid is
Options
- A30 mA
- B60 mA
- C3 A
- D6 A
Correct answer
C. 3 A
Step-by-step solution
For solenoid, the magnetic field needed to be magnetised the magnet. B = μ 0 n I where, n = 100 , l = 10   cm = 10 100   m = 0 . 1   m ⇒ 3 × 10 3 = 100 0 . 1 × I ⇒ I = 3   A