Physics · MU Sofia

16. Magnetic field Magnetic field of a permanent magnet.

Covers the field lines of a permanent magnet running from north to south pole, and how a charged particle's magnetic force depends on its charge, velocity, field strength and the angle between velocity and field. Goes on to motion in a uniform field, the Lorentz force formula with its terms defined, the mass spectrometer, solenoids, Ampere's Law, and fields around circular conductors and solenoids. Includes several pictures showing the motion and devices.

Inside: 2 sections · 7 labelled pictures · 12 flashcards · 3 min

Topic 17 of 42 in the MU Sofia syllabus for Physics (Dental Medicine, Year 1). The free AceMed note covers it in 2 sections, about 504 words (3 min of reading), with 12 flashcards.

In this note

  1. Introduction
  2. Lorentz Force Formula F= q(E+v*B)

Introduction

Summary

  • Magnetic fields, whether from permanent magnets or electromagnets, are delineated by field lines extending from the north to the south pole. Charged particles' behavior in these fields depends on their velocity and the angle of approach, affecting the magnetic force they experience. This concept is crucial in applications like mass spectrometers for ion separation based on mass-to-charge ratios and solenoids that generate magnetic fields with electric current. Ampere's Law connects the magnetic field in a loop to the current passing through it, integral for understanding magnetic fields around conductors. The Lorentz force equation, indicating the combined electric and magnetic forces on charged particles, further elucidates the interaction between charged particles and these fields.

Magnetic Field of a Permanent Magnet

  • Field Lines: Stretch from the north to the south pole.
  • Particle Motion: No magnetic force (Fb = 0) when a particle moves parallel or antiparallel to the magnetic field. The magnetic force (Fb = qvB\sin\theta\) depends on the charge (q), velocity (v), magnetic field (B), and angle (theta) between (v) and (B).
  • Motion in Uniform Magnetic Field:
  • The force (F) on a charged particle equals (m)(a.c) (centripetal acceleration).
  • The period of motion (T), or time for one revolution, is

What Is Lorentz Force?

  • Lorentz force is defined as the combination of the magnetic and electric force on a point charge due to electromagnetic fields. It is used in electromagnetism and is also known as electromagnetic force. In the year 1895, Hendrik Lorentz derived the modern formula of Lorentz force.

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