24.3 Charged particles in circular orbits

A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, the particle will ____:

• move in a straight line

• follow a spiral path

• move along a parabolic path

• move along a waveform

• follow a circular path

Tags

NGSS.HS-PS3-5

A small object with a charge of 𝑞 = +3.0 μ𝐶 and a mass 𝑚 = 2.0 × 10^-6 𝑘𝑔 enters a magnetic field of magnitude 𝐵 = 0.20 𝑇 directed into the page, as shown in the figure below. If the speed of the object is 1000 𝑚/𝑠, the object’s acceleration at the moment it enters the field is most nearly ______.

• zero because the velocity is perpendicular to the magnetic field

• 300 m/s² toward the bottom of the page

• 300 m/s² toward the top of the page

• 600 m/s² toward the bottom of the page

• 600 m/s² toward the top of the page

Tags

NGSS.HS-PS2-1

A particle carrying a charge of +e travels in a circular path in a uniform magnetic field. If instead the particle carried a charge of +2e, the radius of the circular path would have been ____.

• twice the original radius

• four times the original radius

• the same as the original radius

• one-half the original radius

• one-fourth the original radius

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A stationary proton is in a uniform magnetic field of 0.20 T. What is the magnitude of the magnetic force on the proton?

• zero

• 1.6 × 10^-21 𝑁

• 3.2 × 10^-21 𝑁

• 1.6 × 10^-20 𝑁

• 3.2 × 10^-20 𝑁

Tags

NGSS.HS-PS3-5

A proton travels at a speed of 5.0 × 10⁷ 𝑚/𝑠 through a 1.0 𝑇 magnetic field. What is the magnitude of the magnetic force which acts on the proton if the angle between the proton's velocity and the magnetic field vector is 30°?

• 2.0×10^-14 𝑁

• 4.0×10^-14 𝑁

• 2.0×10^-12 𝑁

• 4.0×10^-12 𝑁

• 6.0×10^-12 𝑁

A charged particle of mass 𝑚 is exposed to a constant magnetic field of magnitude 𝐵 and directed out of the page, in which the particle moves in a clockwise circle of radius 𝑅 with a speed 𝑣, as shown below.

In a separate experiment, the same particle is traveling with a speed 2𝑣 in a constant magnetic field of the same magnitude 𝐵, now directed into the page. Which of the following statements is true?

• Now the particle travels in a clockwise circle of radius R

• Now the particle travels in a counterclockwise circle of radius R

• Now the particle travels in a counterclockwise circle of radius 2R

• Now the particle travels in a clockwise circle of radius R/2

• Now the particle travels in a counterclockwise circle of radius R/2

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Uniform magnetic and electric fields exist between the two oppositely charged parallel plates shown in the figure below. An electron travels horizontally between the plates. Assuming gravitational effects to be negligible, which of the following diagrams shows a combination of electric and magnetic field directions that will allow the electron to travel un-deflected?

• 
• 
• 
• 
• 

Tags

NGSS.HS-PS2-5

A beam of electrons has speed 10⁷ 𝑚/𝑠. It is desired to use the magnetic field of the Earth,

5 × 10^-5 𝑇, to bend the electron beam into a circle. What will the radius of this circle be?

• 1 nm

• 1 μm

• 1 mm

• 1 m

• 1 km

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Four small particles are seen moving through an area with the magnetic field going out of the page. Which of the following statements is consistent with the diagram?

• All the particles are positively charges but have different mass

• All the particles have same mass, but different charges

• Two particles are positive while one is negative

• Two particles are negative while one is positive

• You can only ascertain that all are charged

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A particle of charge 𝑞 and mass 𝑚 is moving through a region of space at right angles to an electric field and a magnetic field, where the crossed fields produce a zero net force on the charge. If the speed of the charge is doubled, which of the following will again produce a zero net force on the charge?

I. Reducing the electric field to 𝐸/2

II. Increasing the electric field to 4𝐸

III. Reducing the magnetic field to 𝐵/2

IV. Increasing the magnetic field to 2𝐵

• I only

• II only

• III only

• II and III only

• I and IV only