Lorentz Force Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. The law that governs the interaction of the electromagnetic field with charged matter is

1. Faraday's Law
2. Gauss's Law
3. Lorentz force Law
4. Ampere's Law

Ans. The correct answer is c. Lorentz force Law

Explanation: The interaction of the electromagnetic field with charged matter is governed by the Lorentz force law.

Ques. Lorentz force has direction

1. Parallel to the direction of the moving charge and the magnetic field.
2. Perpendicular to the direction of the moving charge and the magnetic field.
3. scalar quantity
4. None of the above

Ans. The correct answer is b. perpendicular to the direction of the moving charge and the magnetic field.

Explanation: Lorentz force acts perpendicular to the direction of the moving charge and magnetic field. The right-hand rule (Lorentz Force right-hand rule) effectively explains the Lorentz force direction.

Ques. A charged particle moves through a magnetic field perpendicular to its direction. Then

1. The linear momentum changes but the kinetic energy is constant
2. Kinetic energy changes but the momentum is constant
3. Both linear momentum and kinetic energy of the particle are constant
4. Both linear momentum and kinetic energy of the particle are not constant

Ans. The correct answer is a. The linear momentum changes but the kinetic energy is constant

Explanation: The path of motion is circular when a charged particle enters a magnetic field in a direction perpendicular to the direction of motion. The direction of velocity changes at each point in circular motion (the magnitude remains constant). As a result, the tangential momentum will change at every point. However, kinetic energy remains constant.

Ques. A charged particle moving in a magnetic field experiences a resultant force

1. In the direction opposite to that of its velocity
2. In the direction opposite to that of the field
3. In the direction parallel to the field
4. In the direction perpendicular to both the field and its velocity

Ans. The correct answer is d. In the direction perpendicular to both the field and its velocity

Explanation: The force acting on a charged particle having charge q moving with velocity v in a magnetic field B is given by

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

Therefore the direction of the resultant force is perpendicular to both the field and its velocity.

Ques. An α-particle moves from east to west in a magnetic field perpendicular to the plane of the paper and into the paper. The particle is deflected towards

1. North
2. East
3. South
4. West

Ans. The correct answer is c. South

Explanation: A positively charged particle is referred to as an α-particle. The current flows in the direction of the α-particle's motion (east to west). The magnetic field is pointing into the paper. As a result, the force is directed southward by applying Fleming's left-hand rule. As a result, the particle will be deflected to the south.

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Short Answers Questions [2 Marks Questions]

Ques. What is the Lorentz force?

Ans. The Lorentz force is the combination of electric and magnetic forces exerted on a charged point particle by electromagnetic fields. In other terms, the Lorentz force is the force exerted on a charged particle moving through an electric and magnetic field.

Ques. What is the formula to calculate the Lorentz force?

Ans. The formula to calculate the Lorentz force is given by

F = q(E + v x B)

Where

• F is the Lorenz force acting on the charged particle
• q is the charge on the particle
• E is the electric field
• B is the magnetic field
• v is the velocity of the charged particle

Ques. What is the role of the Lorentz force in cathode ray televisions?

Ans. The concept of Lorentz force is used in cathode ray TVs to direct electrons in a straight line so that they arrive at specific points on the screen.

Ques. Define electromagnetism.

Ans. Electromagnetism is the interaction of particles with electric charges through electromagnetic fields. The electromagnetic force is one of nature's four basic forces. It is the most powerful force in atom-molecule interactions.

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Long Answers Questions [3 Marks Questions]

Ques. Which are the familiar devices that use the Lorentz force?

Ans. The familiar devices that use the Lorentz force are

• The Lorentz force is used in magnetrons, cyclotrons, and other circular path particle accelerators, mass spectrometers, velocity filters, and Lorentz force velocimetry.
• Many electrical devices, such as electric motors, railguns, linear motors, loudspeakers, magnetoplasmadynamic thrusters, loudspeakers, homopolar generators, electrical generators, and linear alternators, exhibit this force in its manifestation as the Laplace force on a current in a conductor.

Ques. How do particle accelerators utilize the Lorentz force?

Ans. The fact that charged particles have circular orbits when magnetic field B and the direction of velocity of the charged particle v are perpendicular to each other is taken advantage of by particle accelerators like cyclotrons. 

• A perfectly generated electric field provides the charged particles with additional kinetic energy for each rotation. 
• This allows them to move in larger orbits. 
• These particles may be used in a variety of different ways when they have the ideal energy. It is used in a variety of medical procedures and the research of subatomic particles.

Ques. What is the significance of the Lorentz force?

Ans. The following are the significance of the Lorentz force

• The production of electric and magnetic fields by moving charge and current carriers or charge carriers may be described using the modern Maxwell's equations. By explaining the force acting on a point charge q moving in the presence of an electromagnetic field, Lorentz's equation of force completes this picture.
• The effects of electric field E and magnetic field B on point charges are described by Lorentz's equation of force, however, these electromagnetic forces do not provide a comprehensive picture.
• The response of a point charge to Lorentz's equation is one thing, but using charges and current to produce electric and magnetic fields is another. Both theoretically and computationally, the Lorentz force is insufficient for describing the collective behavior of charge carriers in actual materials.

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Very Long Answers Questions [5 Marks Questions]

Ques. What is the main drawback of the concept of the Lorentz force?

Ans. The effect of magnetic field (B) and electric field (E) on a point electric charge is described by the Lorentz force. 

• Such electromagnetic forces, however, do not provide a complete picture. 
• Most likely, the nuclear force and gravity are connected to electrically charged particles. 
• Therefore, although the Maxwell equations are connected to other physical laws through current densities and charge, they do exist independently from those laws. 
• The Lorentz force is insufficient in actual substances to account for the general behavior of the point particles, both computationally and theoretically. 
• These particles not only respond to the magnetic and electric fields in a material medium, but they also generate such fields.

Ques. What are the applications of Lorentz force?

Ans. The following are the applications of Lorentz force

• The Lorentz force is used by cyclotrons and other particle accelerators. 
• The graph needed to determine the courses of charged particles is produced in a bubble chamber using the Lorentz force. 
• The Lorentz force is used in cathode ray TVs to direct electrons in a straight line so that they land at certain spots on the screen.
• Particle accelerators, mass spectrometers, magnetrons, velocity filters, and Lorentz force calorimetry are examples of electric devices that use the Lorentz force.
• Many electrical devices, such as electric motors, railguns, linear motors, loudspeakers, magnetoplasmadynamic thrusters, loudspeakers, homopolar generators, electrical generators, and linear alternators, exhibit this force in its manifestation as the Laplace force on a current in a conductor.

Ques. What are the properties of Lorentz force?

Ans. The following are the properties of Lorentz force

• If the direction of the motion of the particle (v), electric field (E), and magnetic field (B) are parallel to each other, then for the constant value of the electric and magnetic field, the magnetic force on the charged particle is given by

F_B = qv sin0 = 0

As a result, the charge will perform a rectilinear motion since it is accelerated by the electric field.

• If the magnetic and electric fields are parallel to one another and the direction of the motion of the particle is perpendicular to the electric and magnetic field, then

F_B ≠ 0

As a result, the charge will perform a circular motion since it is accelerated by the electric field.

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