NEET Physics Notes Magnetic Effects of Current – Concept of Magnetic Field
Concept of Magnetic Field
Concept of Magnetic Field
In 1820, Oersted observed that a compass needle suffers, a deflection when brought near a current carrying wire. This means that, electric current, that is electric charge in motion, gives rise to magnetism.
Oersted’s Experiment
Oersted found experimentally, that a magnetic field is established around a current carrying conductor just as it occurs around a magnet.
Biot-Savart’s Law and its Applications
According to Biot-Savart’s law, the magnetic field dB at a point P, due to a current element I dl is given by
Here,
is a proportionality constant, having a value of 10_7TmA_1 in free space.
The term 
is known as the magnetic permeability of free space, where 
. Dimensional formula for is [MLT-2A-2].
Direction of magnetic field produced due to a current carrying straight wire can be obtained by the Right hand thumb rule.
According to right hand thumb rule grasp the wire carrying current in your right hand with your extended thumb pointing in the direction of current. Then, the fingers will curl around in the direction of the magnetic field.
Magnetic Field due to Circular Current Loop
If there is a circular coil of radius R and N number of turns, carrying a current / through the turns, then magnetic field at the centre of coil is given by
If there is a circular arc of wire subtending an angle θ at the centre of arc, then the magnetic field at the centre point
At a point O situated at a distance r from centre of a current carrying circular coil along its axial line. The magnetic field is
