Magnetic field due to current carrying conductor - class-XII

The magnetic field are concentric circle at point of a current carrying circular conductor direction of the magnetic field of every section of the circular loop can be found by using the right hand thumb rule .if you curl your right hand fingers in direction of magnetic field your thumb will point in the direction of the current flow.

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.

Electric current and magnetism are very closely related phenomenon and both can be generated using the other.

Electromagnetism is study of various phenomenon related to electricity and magnetism. 

Electric current and magnetism are very closely related phenomenon and both can be generated using the other.

Direction of magnetic field lines around a current carrying conductor can be found by RIght Hand Thumb Rule.

According to the right-hand rule, the magnetic field lines around a straight current-carrying conductor form concentric circles centered on the wire.

According to the Biot Savart's law, a current carrying conductor produces a magnetic field in its surroundings. This will cause the helix to oscillate across a mean position.

A charged particle produces an electric field around it independent of its motion. But when it is at rest, it doesn't produce a magnetic field. 

According to the right-hand thumb rule, the magnetic field lines around a long straight current-carrying conductor are concentric circles centered on the wire.

Answer is D.

A solenoid is an electromagnet. That is, it acts as a bar magnet only when electricity is passed through it. Its purpose is to generate a controlled magnetic field. 
A solenoid is a coil of insulated or enameled wire wound on a rod shaped form made of solid iron solid steel or powdered iron.

In his experiment Oersted observed that the deflection of the needle compass changed according to the direction of the current and also as the current in the wire increased, the deflection of the needle increased. Thus he inferred that the strength and direction of the magnetic field depends on the magnitude and direction of current.

Heating effect and lighting effect does not depend on the direction of current.

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept in close proximity of an electric wire carrying current it showed deflections in the east and west direction depending on the direction of current. Thus, indicating that the strength and direction of the magnetic field depends on the magnitude and direction of the current.

In his experiment Oersted observed that as the current in the wire increased, the deflection of the needle also increased, indicating that they are directly proportional.

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept below the wire and current was passed from A to B the north pole of the needle deflected towards the west and on reversing the direction of the current from B to A, it deflected towards the east. Similarly, when the needle was kept above the wire and current was passed from A to B the north pole of the needle deflected towards the east and on reversing the direction of the current from B to A, it deflected towards the west. This indicates that the direction of the magnetic field depends on the direction of current.

The earth acts like a huge magnet. Thus in the absence of electric current a compass needle always comes to rest in Earths North-south direction. However, when current passes through the circuit the needle comes to rests in the direction opposite to the magnetic field of Earth i.e. South-North direction.

If electric current is passed through metal body then it behaves as magnet. passing an electric current through iron does not produce a magnet. But if you pass a direct current through a coil wound around the piece of iron, you will magnetize it. Passing a direct electric current through the same coil with no iron inside the coil will still produce a magnetic field that behaves just like a magnet. Similarly, passing a direct current through a coil around a piece of Bismuth will create the same magnetic field which behaves just like a magnet.

Oersted discovered the relationship between electricity and magnetism.

The logical sequence for calculating the resultant magnetic field is: identify values, write the formula, determine individual fields (B1 and B2), determine directions, and then sum or subtract based on those directions.