The magnetic induction inside a solenoid is 6.5×10–4T. When it is filled with iron medium then the induction becomes 1.4T. The relative permeability of iron will be-

1578   2355 1836 2154

2154

$\mu_r = \frac{B}{B_0} = \frac{1.4}{6.5\times 10^{-4}} = 2154$