What are electromagnets?

Statement-$1$: Ampere's law can be used to find the magnetic field due to a finite length of a straight current-carrying wire.
Statement-$2$: The magnetic field due to a finite length of a straight current-carrying wire is symmetric about the wire.

$A$ solenoid has $N$ turns,length $l$,and cross-sectional radius $r$. If a current $i$ flows through the solenoid,what is the magnetic field at the axial midpoint? (Given $l \simeq r$)

$A$ winding wire which is used to frame a solenoid can bear a maximum $10\, A$ current. If the length of the solenoid is $80\, cm$ and its cross-sectional radius is $3\, cm$,then the required length of the winding wire is $(B = 0.2\, T)$.

Ampere's circuital law is associated with which law?

An infinitely long hollow conducting cylinder with inner radius $R/2$ and outer radius $R$ carries a uniform current density along its length. The magnitude of the magnetic field,$|\vec B |$ as a function of the radial distance $r$ from the axis is best represented by: