Tag: physics

Using Right Hand thumb rule, as current direction reverses, you need to reverse the hand and direction of magnetic field reverses.

Using Ampere's Law for an infinite cylinder, the magnetic field at a point inside is determined by the current enclosed. The vector direction is perpendicular to the radial vector from the axis.

For a circular loop of radius R carrying current, I placed in $x-y$ plane, the magnetic moment $M= I\,\,\pi R^2$. It acts perpendicular to the loop i.e., along with the z-direction. When half of the current loop is bent in y-z plane, the magnetic moment due to half current loop in x-y plane,$ M _1 = I \left (\dfrac {\pi R^2}{2} \right )$ acting along z-direction.
Magnetic moment due to half current loop in y-z plane,$ M _2 = I \left (\dfrac {\pi R^2}{2} \right )$ along x-direction.
Effective magnetic moment due to entire bent current loop,
$M'$ =$\sqrt{{M _{1}^{2}}+ {M _{2}^{2}}} $=$\sqrt {{\left (\dfrac{I \pi R^2}{2} \right )^2}+{\left (\dfrac{I \pi R^2}{2} \right )^2}}$
$M'=\dfrac{I\pi R^2}{2}\sqrt2 <M$
i.e., magnetic moment diminishes.

A Toroid is a solenoid which is bent in the form of a ring with its both the ends joined together.  Since both the ends are merged, it appears endless.

A solenoid is a long coil of wire wrapped in a cylindrical shape, which creates a uniform magnetic field inside when current flows through it.