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Understanding Force on Electric Charges in Magnetic Fields
Explore the fascinating world of electromagnetic forces and their impact on charged particles. Discover key concepts, practical applications, and problem-solving techniques in this comprehensive guide.

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Now Playing:Force on electric charge moving in a magnetic field – Example 0a
Intros
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  1. The magnitude of the electromagnetic force
  2. The direction of the electromagnetic force
Examples
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  1. The path of a charged particle in a uniform magnetic field is circular when the initial velocity is perpendicular to the field.

    Force on Electric Charge Moving in a Magnetic Field


    Which of the following are a valid expression for the radius of this orbit in terms of the magnetic field strength, and the particle's momentum and charge?

    1. BqpBqp
    2. Bpq\frac{Bp}{q}
    3. Bqp\frac{Bq}{p}
    4. pBq\frac{p}{Bq}
    Magnets and magnetic fields 
    Jump to:NotesConceptFAQsPrerequisites
    Notes

    In this lesson, we will learn:

    • Magnitude and direction of an electromagnetic force exerted on moving charge in a magnetic field.
    • The radius of the circular motion of a moving charged particle.

    Notes:

    • A current-carrying wire experience a force when is placed in a magnetic field, similarly, freely moving charged particles would also experience a force when passing through a magnetic field.
    • The magnitude of the electromagnetic force exerted on moving charge in a magnetic field is calculated using the following equation:

      F=qvBsin⁡θF = qvB \sin \theta

    qq = quantity of charge 
    vv = velocity of moving charge 
    BB = magnetic field 
    θ\theta = the angle between B→ \overrightarrow{B} and v→ \overrightarrow{v}

    • The force is greatest when the angle between B→ \overrightarrow{B} and v→ \overrightarrow{v} is 90°, Fmax=qvB \qquad F_{max} = qvB
    • The force is zero if the particle moves parallel to the field lines and the angle between B→ \overrightarrow{B} and v→ \overrightarrow{v} is 0°

    • The direction of the force is perpendicular to the magnetic field B→ \overrightarrow{B} and to the velocity v→ \overrightarrow{v} of the particle. 
    • The direction of the force is found using the right-hand rule, fingers point along the direction of the particle’s velocity and bend your fingers towards the of B→ \overrightarrow{B} . Then your thumb will point in the direction of the force. This is true only for positively charged particles, for negatively charged particles, the force is in exactly the opposite direction.

    Force on Electric Charge Moving in a Magnetic Field

    • The force exerted by a uniform magnetic field on a moving charged particle, produces a circular path.

    “The diagram below represents the direction of the force exerted on an electron”


    Force on Electric Charge Moving in a Magnetic Field

    • The particle would move in a circular path with constant centripetal acceleration if the force is always perpendicular to its velocity, a=v2ra = \frac{v^{2}}{r}
    • The force is greatest when the angle between B→ \overrightarrow{B} and v→ \overrightarrow{v} is 90°, Fmax=qvB \qquad F_{max} = qvB


      • ∑F=ma \sum F = ma

      qvB=mv2rqvB = m \frac{v^{2}}{r}

      r=mvqB r = \frac{mv} {qB}

      Since F→ \overrightarrow{F} is perpendicular to v→ \overrightarrow{v} , the magnitude of v→ \overrightarrow{v} does not change. From this equation, we see that if B→ \overrightarrow{B} = constant, then rr = constant, and the curve must be a circle.
    Concept

    Introduction to Force on Moving Electric Charges in Magnetic Fields

    Welcome to our exploration of the fascinating world of electromagnetic forces! Today, we'll dive into the concept of force on electric charges moving through magnetic fields. This fundamental principle is crucial in understanding how electromagnetic forces shape our universe. Our introduction video provides a clear, visual explanation of this concept, making it easier to grasp. As we begin, imagine a charged particle zipping through space, suddenly encountering a magnetic field. What happens next? That's exactly what we'll uncover! This interaction between moving charges and magnetic fields is the basis for many technological applications, from electric motors to particle accelerators. By understanding this concept, you'll gain insight into how electromagnetic forces influence the behavior of charged particles in various contexts. So, let's embark on this exciting journey together and unravel the mysteries of electromagnetic forces!

    Understanding the force on electric charges is essential for comprehending the broader implications of electromagnetic theory. The interaction between moving charges and magnetic fields not only explains natural phenomena but also drives innovation in technology. From the development of new medical imaging techniques to advancements in communication systems, the principles we explore today have far-reaching impacts. Let's continue to delve deeper into this topic and discover how these forces operate in different scenarios.

    FAQs

    1. What is the Lorentz force?

      The Lorentz force is the force experienced by a charged particle moving in a magnetic field. It is given by the equation F = qvB sin θ, where F is the force, q is the charge of the particle, v is its velocity, B is the magnetic field strength, and θ is the angle between the velocity and magnetic field vectors. This force is responsible for the curved path of charged particles in magnetic fields.

    2. How does the right-hand rule work for determining the direction of force on a moving charge?

      The right-hand rule is a method to determine the direction of the force on a positively charged particle moving in a magnetic field. Point your thumb in the direction of the particle's velocity, your index finger in the direction of the magnetic field, and your middle finger (perpendicular to both) will then point in the direction of the force. For negatively charged particles, the force direction is opposite to what the right-hand rule indicates.

    3. Why do charged particles move in circular paths in uniform magnetic fields?

      Charged particles move in circular paths in uniform magnetic fields because the magnetic force acts perpendicular to both the particle's velocity and the magnetic field lines. This perpendicular force causes continuous change in the direction of motion without changing the speed, resulting in a circular path. The radius of this path depends on the particle's mass, charge, velocity, and the magnetic field strength.

    4. What are some practical applications of the force on moving charges in magnetic fields?

      This principle has numerous applications, including: 1) Particle accelerators for scientific research, 2) Mass spectrometers for chemical analysis, 3) Hall effect sensors for position and speed detection in various devices, 4) Cyclotrons for medical treatments and isotope production, and 5) Ion engines for spacecraft propulsion. These applications demonstrate the wide-ranging impact of this fundamental electromagnetic principle.

    5. How does the strength of the magnetic field affect the force on a moving charge?

      The strength of the magnetic field directly affects the force on a moving charge. According to the equation F = qvB sin θ, the force is directly proportional to the magnetic field strength (B). This means that doubling the magnetic field strength will double the force on the charged particle, assuming all other factors remain constant. This relationship is crucial in designing and controlling devices that utilize electromagnetic forces.

    Prerequisites

    Understanding the force on an electric charge moving in a magnetic field is a crucial concept in physics, particularly in electromagnetism. While there are no specific prerequisite topics provided for this subject, it's important to recognize that a strong foundation in basic physics and mathematics is essential for grasping this complex phenomenon.

    To fully comprehend the force on an electric charge moving in a magnetic field, students should have a solid understanding of fundamental physics concepts such as vectors, forces, and motion. These basic principles form the backbone of more advanced topics in electromagnetism.

    Additionally, a good grasp of electric charges and electric fields is crucial. Understanding how charged particles behave and interact with their surroundings lays the groundwork for exploring their behavior in magnetic fields. Students should be familiar with concepts like Coulomb's law and the properties of electric fields before delving into magnetic interactions.

    Knowledge of magnetism and magnetic fields is equally important. Students should be comfortable with the idea of magnetic field lines, the concept of magnetic flux, and how magnetic fields are generated by moving charges or current-carrying conductors.

    A solid foundation in vector calculus is also beneficial, as it allows for a more rigorous mathematical treatment of the forces involved. Concepts such as cross products and vector operations are frequently used in describing the force on a moving charge in a magnetic field.

    Furthermore, familiarity with electromagnetic induction and Faraday's law can provide valuable context for understanding the interplay between electric and magnetic fields. These concepts help explain how changing magnetic fields can induce electric fields and vice versa.

    While not directly related, a basic understanding of special relativity can offer interesting insights into the relationship between electricity and magnetism. It helps explain how magnetic forces can be viewed as relativistic effects of electric forces.

    By building a strong foundation in these prerequisite areas, students will be better equipped to tackle the complexities of forces on moving charges in magnetic fields. This knowledge will enable them to understand phenomena such as the Lorentz force, cyclotron motion, and the Hall effect, which have numerous practical applications in modern technology.

    In conclusion, while there are no specific prerequisites listed for this topic, a comprehensive understanding of basic physics, electromagnetism, and related mathematical concepts is crucial for mastering the subject of force on electric charges moving in magnetic fields. This foundational knowledge will not only aid in understanding the topic at hand but also pave the way for exploring more advanced concepts in electromagnetism and physics as a whole.