A telephonic cable at a place has four long straight horizontal wires carrying a current of `1.0amp.` in the same direction east to west. The earth's magnetic field at the place is `0.39G` and the angle of dip is `35^@`. The magnetic declination is almost zero. What are the resultant magnetic fields at points `4.0cm` below and above the cable?

Explanation

The vertical component of earth's magnetic field is given as:
`H_(v)+H sin delta`
`=0.39 sin35^(@)=0.22G`
The angle made by the field with its horizontal component is given as:
`theta=tan^(-1)(H_(v))/(H_(b))`
` = tan^(-1)(0.22)/(0.12)=61.39^(@)`
The resultant field at the point is given as:
`H_(1)=sqrt((H_(x))^(2)+(H_(b))^(2))`
`=sqrt((0.22)^(2)+(0.12)^(2))=0.25G`