JEE Main 2014 · 6 Apr · Shift 1 · Physics Q20

← JEE Main 2014 · 6 Apr · Shift 1

PhysicsSingle correct+4 / -1Question 20 of 90

The coercivity of a small magnet where the ferromagnet gets demagnetized is $3\times10^3$ 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 :

30 mA

60 mA

3 A

6 A

Answer and worked solution

Official answer: C

The solenoid's field intensity must reach the coercivity:
$H=nI,\quad n=\frac{100}{0.1}=1000\text{ m}^{-1}\implies I=\frac{3\times10^3}{1000}=3\text{ A}.$

Topics:Hysteresis Ampere's circuital law

← Previous question Next question →

JEE Main 2014 · 6 Apr · Shift 1, Physics question 20