Q.

The percentage increase in magnetic field (B) when space within a current carrying solenoid is filled with magnesium (magnetic susceptibility χmg=1.2×10–5) is          [2025]

1 65×10–3%  
2 56×10–5%  
3 56×10–4%  
4 53×10–5%  

Ans.

(1)

% change in B=△BB%=Bnew–BoldBold×100%

                               =μni–μ0niμ0ni×100%=(μ–μ0)μ0×100%

                               =(μ0μr–μ0)μ0×100%

                                =(μr–1)×100%

                                =χn×100%=1.2×10–3%