Two toroids with number of turns 400 and 200 have arrange radii respectively 30 cm and 60 cm . If they carry…
Two toroids with number of turns 400 and 200 have arrange radii respectively 30 cm and 60 cm . If they carry the same current, the ratio of magnetic fields in these two toroids is
2:1
1:4
2:3
4:1
Solution
For toroid, magnetic field inside it is
$\begin{aligned}
& B=\mu_0\left(\frac{N}{2 \pi R}\right) \cdot I \Rightarrow B \propto \frac{N}{R} \\
& \therefore \frac{B_1}{B_2}=\left(\frac{N_1}{N_2}\right)=\frac{400}{200} \times \frac{60}{30}=4: 1
\end{aligned}$