Magnetic Field Due To Current In Straight Wire - Practice Questions & MCQ

Magnetic Field due to current in straight wire:

Magnetic field lines around a current carrying straight wire are concentric circles whose centre lies on the wire.

Magnitude of magnetic field B, produced by straight current carrying wire at a given point  is directly  proportional to current I pairing through the wire i.e.    . B is inversely proportional to the distance 'r' from wire.

Magnetic field due to a current carrying wire at a point P which lies at a perpendicular distance r from the
wire as shown is given as: 

From figure ,  

Hence,     

Different cases: 

Case 1 : When the linear conductor XY is of finite length and the point P lies on it's perpendicular bisector as shown

Case 2 : When the linear conductor XY is of infinite length and the point P lies near the centre of the conductor

Case 3 : When the linear conductor is of infinite length and the point P lies near the end Y or X

• When point P lies on axial position of current carrying conductor then magnetic field at P, B=0.
• The value of magnetic field induction at a point, on the centre of separation of two linear parallel conductors carrying equal currents in the same direction is zero.
• If direction of current in straight wire the known then direction of magnetic field produced by straight wire carrying current is obtained by maxwell's right hand  thumb rule.