(a) Draw magnetic field lines produced around a current carrying straight conductor
passing through a cardboard. Name, state and apply the rule to mark the direction
of thers field lines.
(b) How will the strength of the magnetic field change when the point where magnetic
field is to be determined is moved away from the straight wire carrying constant
current? Justify your answer?

Explanation

To mark the direction of magnetic field lines, we will use the Right hand thumb rule.
If the current carrying straight conductor is held in the right hand in such a way that
the thumb points towards the direction of current, then your fingers will wrap around
the conductor in the direction of the field lines.

(b) `*` The strength of the magnetic field decreases when the point where magnetic field is
to be determined in moved away from a straight wire carrying constant current.
`*` The strength of the magnetic field is inversely proportional to the distance from the
origin. As the distance increases the strength decreases.