Table of Contents
Chapter 4 Moving Charges and Magnetism Class 12 Physics Hand Written Notes By Ashish Anand Sir
Class 12 Physics Revision Notes Chapter 4 Moving Charges and Magnetism
Biot – Savart law: The magnitude of Magnetic Field
- Magnetic field due to long straight current carrying conductor:
- If conductor is infinitely long,
- Right-hand rule is used to find the direction of magnetic field due to straight current carrying conductor.
- Force on a Straight Conductor: Force F on a straight conductor of length
and carrying a steady current I placed in a uniform external magnetic field B,
- Lorentz Force: Force on a charge q moving with velocity v in the presence of magnetic and electric fields B and E.
- Magnetic Force: The magnetic force
is normal to
and work done by it, is zero.
- Cyclotron: A charge q executes a circular orbit in a plane normal with frequency called the cyclotron frequency given by,
This cyclotron frequency is independent of the particle’s speed and radius. - Magnetic Field due to Circular current carrying Coil: Magnetic field due to circular coil of radius ‘a’ carrying a current I at an axial distance r from the centre-
At the centre of the coil, - Ampere’s Circuital Law: For an open surface S bounded by a loop C, then the Ampere’s law states that
where I refers to the current passing through S.
- If B is directed along the tangent to every point on the perimeter, then
Where Ie is the net current enclosed by the closed circuit.
- Magnetic Field: Magnetic field at a distance R from a long, straight wire carrying a current I is given by,
The field lines are circles concentric with the wire. - Magnetic field B inside a long Solenoid carrying a current I:
Where n is the number of turns per unit length.
- For a toroid,
Where N is the total numbers of turns and r is the average radius.
- Magnetic Moment of a Planar Loop: Magnetic moment m of a planar loop carrying a current I, having N closely wound turns, and an area A, is
- Direction of
is given by the Right – Hand Thumb Rule: Curl and palm of your right hand along the loop with the fingers pointing in the direction of the current, the thumb sticking out gives the direction of
- Loop placed in a Uniform Magnetic Field:
- When this loop is placed in a uniform magnetic field B, Then, the force F on it is, F = 0
And the torque on it is
In a moving coil galvanometer, this torque is balanced by a counter torque due to a spring, yielding.Where
is the equilibrium deflection and k is the torsion constant of the spring.
- Magnetic Moment in an Electron: An electron moving around the central nucleus has a magnetic moment , given by
Where
- Bohr Magneton: The smallest value of
is called the Bohr magneton μBOr
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