Question

The magnetic induction inside a solenoid is $6.5\times {10}^{-4}$T. When it is filled with iron medium then the induction becomes 1.4 T. The relative permeability of iron will be

• A. 2154
• B. 2355
• C. 1578
• D. 1836

Answer 1

The correct option is A 2154

Relative permeability

Magnetic Induction inside solenoid without iron core
$B_0={\mu }_{0}nI=6.5\times {10}^{-4}$ T
(n = no. Of turns per unit length, I = current in solenoid)

Magnetic induction after filling Iron medium
$B=\mu nI=1.4T$
Relative permeability of iron,

${\mu }_r=\frac{\mu }{{\mu }_0}=\frac{B}{B_0}=\frac{1.4T}{6.5\times {10}^{-4}T}=2154$

Hence the correct option is (D)