A high current power line is aligned from geographic south t

A high current power line is aligned from geographic south to north. your compass is 80 cm directly under it. The earth\'s magnetic field at this location is known to be 30 mu T at 12 degree east of true geographic north. The actual current (electrons) in the power line is 280 A travelling south. Determine the direction your compass needle will point and the strength of the net Magnetic Field at that point:

Solution

Magnetic field due to current , Bc= u*I/(2*pi*r)

So, Bc = 1.26*10^-6*280/(2*pi*0.8)

= 7.02*10^-5 T directed towards west.

Magnetic field of earth ,Be = 30*10^-6 T directed 12 deg east of North

So, net magnetic field = sqrt((70-30*sin(12 deg))^2+(30*cos(12 deg))^2)

= 70.2*10^-6 T <------ magnitude of magnetic field

Direction = atan((30*cos(12 deg))/(70- 30*sin(12deg)))

= 90 - 24.7 = 65.3 deg West of north.