MHT CET Medical202622 April 2026Evening ShiftPhysicsMagnetic Effects of CurrentActual
A long straight wire along the z -axis carries a current ' I ' in the negative z-direction. The magnetic induction ' B ' at a point having co-ordinates (x, y) on the z = 0 plane is
Options
- A₀ I(y i - x j ) 2 (x^2 + y^2)
- B₀ I(x i + y j ) 2 (x^2 + y^2)
- C₀ I(x j - y i ) 2 (x^2 + y^2)
- D₀ I(x i - y j ) 2 (x^2 + y^2)
Correct answer
A. ₀ I(y i - x j ) 2 (x^2 + y^2)
Step-by-step solution
The magnetic field due to a long straight wire carrying current I is given by: B = ₀ I 2 d ( u n ) where u is the unit vector along the direction of current, d is the perpendicular distance from the wire, and n is the unit vector along the position vector of the point with respect to the wire. Since the current is in the negative z-direction, u = - k . The position vector of the point (x, y) on the z = 0 plane is r = x i + y j . The distance of the point from the wire is d = | r | = x^2 + y^2 . The unit vector n =