Do you know solenoid? Can you compare the magnetic field due to a current carrying solenoid with that due to a bar magnet? . 
 

Using electrostatic analogue, obtain the magnetic field at a distance $x$ on the perpendicular bisector of a magnetic dipole 

$\overrightarrow{\mathrm{m}}$ .For $\mathrm{x}\gg \mathrm{R}\text{, verify that }\overrightarrow{\mathrm{B}}=\frac{{\mathrm{\mu }}_0}{4\mathrm{\pi }}\frac{\mathrm{m}}{{\mathrm{x}}^3}$

A conductor has 3 segments: two starlight and of length L each and a semicircular with radius R. It carries a current I. What is the magnetic field B at point P?

Figure a, b show two Amperian loops associated with the conductors carrying current I in the sense shown. The $\text{∮}\overrightarrow{\mathrm{B}}\cdot \mathrm{d}\overrightarrow{\mathrm{l}}$in the cases a and b will be, will be respectively,