Question

Draw a diagram showing the direction of the magnetic field lines due to a straight wire carrying current. Also show the direction of current in the wire.

Answer 1

When electric current flows through a conductor, an induced EMF is created which in turn creates a magnetic field around it. The magnetic field lines form concentric circles around the conductor. The direction of the magnetic field is perpendicular to the wire and is in the direction of wrapped fingers of the right hand holding the conductor and the thumb pointing upwards indicates the direction of the current.
A magnetic field implies the existence of poles and the polarity of a current carrying conductor is north-south when the current flows in the anti-clockwise direction. When magnetic compass with the north end is brought closer to the 1st end of the conductor, the needle deflects towards the west, that is away from the conductor because the magnetic compass that is pointing in the direction of the earth's magnetic field, i.e. north- south direction repels with the north pole of current carrying conductor. Like poles repel each other. This is the fundamental principle of magnetism.