NEET2004PhysicsMagnetic Effects of CurrentActual
A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from the center of the coil, such that r>>R , varies as
Options
- A1 / r
- B1 / r^ 3 / 2
- C1 / r^2
- D1 / r^3 .
Correct answer
D. 1 / r^3 .
Step-by-step solution
Magnetic field at a point on the axis of a loop is given by B= ₀ 4 2 I R^2 (R^2+r^2 )^ 3 / 2 When r>>R , B= ₀ 4 2 R^2 I r^3 = ₀ 2 A I r^3 . Thus, B (1 / r^3 ) .