A long straight wire in the horizontal plane carries a current of 50A in north to south direction. Give the magnitude and direction of `vecB` at a point `2*5m` east of the wire.

Explanation

Current in the wire, `I = 50 A`
A point is 2.5m away from the East of the wire.
`:.` Magnitude of the distance of the point from the wire, `r = 2.5 m`.
Magnitude of the magnetic field at that point is given by the relation, `B = (mu_(0)2I)/(4pir)`
Where, `mu_(0) =` Permeability of free space `= 4n xx 10^(-7)T mA^(-1)`
`B = (4pi xx 10^(-7) xx 2xx 50)/(4pi xx 2.5)`
`= 4 xx 10^(-6)T`
The point is located normal to the wire length at a distance of 2.5m. The direction of the current in the wire is vertically downward. Hence, according to the Maxwell's right hand thumb rule, the direction of the magnetic field at the given point is vertically upwards.