Magnetism Question 295
Question: 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:
Options:
A) 30 mA
B) 60 mA
C) 3 A
D) 6 A
Show Answer
Answer:
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 $
BETA
