Moving Charges and Magnetism – Class 12 Physics Notes | CBSE NCERT Based

 📚 Chapter: Moving Charges and Magnetism – Class 12 Physics Notes



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🔸 1. Magnetic Force on a Moving Charge


When a charged particle moves in a magnetic field, it experiences a force:


\vec{F} = q (\vec{v} \times \vec{B}) = qvB \sin\theta


Maximum force when 


No force when particle is at rest or 




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🔹 2. Magnetic Force on a Current-Carrying Conductor


\vec{F} = I (\vec{L} \times \vec{B})


Direction of force: given by Right-Hand Rule




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🔹 3. Motion of a Charged Particle in Magnetic Field


Path becomes circular if velocity is perpendicular to B.


Radius of circular path:



r = \frac{mv}{qB}


Time period:



T = \frac{2\pi m}{qB}



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🔹 4. Biot–Savart Law


Gives magnetic field due to a current element:


d\vec{B} = \frac{\mu_0}{4\pi} \frac{I d\vec{l} \times \vec{r}}{r^3}



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🔹 5. Magnetic Field Due to:


Straight wire:



B = \frac{\mu_0 I}{2\pi r}


Circular loop:



B = \frac{\mu_0 I}{2R} \quad \text{(at center)}


Solenoid:



B = \mu_0 n I



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🔹 6. Ampere’s Circuital Law


\oint \vec{B} \cdot d\vec{l} = \mu_0 I_{enclosed}


Used to calculate magnetic field in symmetrical situations.



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🔹 7. Lorentz Force


When both electric and magnetic fields are present:


\vec{F} = q (\vec{E} + \vec{v} \times \vec{B})



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🔹 8. Cyclotron


A device to accelerate charged particles using magnetic field and alternating voltage.


Cyclotron frequency:



f = \frac{qB}{2\pi m}


Used in medical and nuclear fields.



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🔹 9. Torque on Current Loop in Magnetic Field


\vec{\tau} = \vec{m} \times \vec{B}



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🔹 10. Magnetic Dipole in Uniform Magnetic Field


Experiences torque, aligns itself


No net force, only rotation




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📌 Conclusion:


This chapter connects electricity and magnetism. It explains how moving charges generate magnetic fields, and how magnetic fields affect current and charges — formin

g the base of electromagnetism.



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✍️ Written by: Shahid – Study with Shahid

🔗 Visit: https://shahidnotes12.blogspot.com

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