Question

The coils A and B having the radii in the ratio $1:2$ carrying currents in the ratio $5:1$ and have the number of turns in the ratio $1:5$. The ratio of magnetic inductions at their centres is

• A. $1:2$
• B. $2:1$
• C. $1:5$
• D. $5:1$

Answer 1

Answer: (B)

$2:1$

$B=\frac{n{\mu }_{0}i}{2r}$

$B\alpha \frac{ni}{r}$

$\frac{B_1}{B_2}=\frac{n_1{i}_1\cdot r_2}{n_2{i}_2{r}_1}$

$=\left(\frac{1}{5}\right)\left(\frac{5}{1}\right)\left(\frac{2}{1}\right)$

$=2:1$