Question

When equal current is passed through two coils. equal magnetic field is produced at their centers If the ratio of number of turns in the coils is 8:15 then the ratio of their radii will be

• A. 1 : 1
• B. 15 : 8
• C. 8 : 15
• D. 1 : 2

Answer 1

Answer: (C)

8 : 15

Given: $\frac{n_1}{n_2}:\frac{8}{15}$

Solution: By using the formula of magnetic field at the centre of the coil i.e.

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

Now the relation between n & r comes out to be:

$\frac{n_1}{n_2}=\frac{r_1}{r_2}$

$\frac{r_1}{r_2}=\frac{8}{15}$

Hence the correct option is C