Question

magnetic field at the center of a current carrying circular coil of radius 10 cm is 5â5 times the magnetic field at a point on the axis. The distance of the point from the center of the coil is ?
a) 5
b) 10
c) 20
d) 25

Answer 1

20 is the correct answer I hope so.......

Answer 2

"As the formula,

Baxis (x) = μ0ir^2/ 2(x^2 + r^2)^ 3/2

While Bcenter = μ0i/2r

Given, μoi/2r = 5 square root 5 [μ0ir^2/ 2(x^2 + r^2)^ 3/2]

(x^2 + r^2)^3/2 = 5 square root 5 r^3

Squaring on both side,

(x^2 + r^2)^3 = 125 r^6

X^2 + 3^2 = 5r^2

X^2 = 4r^2

X = +_ 2r = 20 cm if we consider that it is positive

"