Question

A current through a horizontal power line flows east to west direction. What is the direction of magnetic field at a point directly below it?

Answer 1

If right hand thumb rule is used , then direction of magnetic field around current carrying conductor can be found out. Right hand thumb rule states that: Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field,
In the question, current is from east to west and hence the direction of the magentic field would be in the directin of the curl of the fingers. This is represented in the diagram shown. Thus, the direction of the magnetic field at a point directly below the horizontal power line is outwards ($P^{\prime }$).