Magnetic effect of a current — Describe

Describe the magnetic field pattern, including direction, around a current-carrying straight wire and around a solenoid.

Around a straight wire, the field forms concentric circles centred on the wire, with direction given by the right-hand grip rule (thumb points along the current, fingers curl in the direction of the field). A solenoid produces a field pattern like that of a bar magnet outside the coil, with field lines emerging from one end (behaving as a N pole) and entering the other (S pole); inside the solenoid the field is strong and uniform, running parallel to the axis. The direction can again be found with the right-hand grip rule, with the curled fingers following the current in the loops and the thumb pointing to the N pole end.