Free Printable Topic 20.3

1-12.

Understanding Magnetic Fields and Charged Particles

Determine the direction of the force on a charge moving in a magnetic field. Use the right-hand rule for positively charged particles: Point your fingers in the direction of velocity, curl them towards the magnetic field, and your thumb will point in the direction of the force. For negatively charged particles, the force direction is opposite to that indicated by the right-hand rule.
Understand the origin of the Hall voltage and derive and use the expression VH=BI/(ntq). The Hall effect occurs when a current-carrying conductor is placed in a magnetic field, resulting in a transverse electric field. Describe the use of a Hall probe to measure magnetic flux density, where the Hall voltage is directly proportional to the magnetic flux density.
Describe the motion of a charged particle moving in a uniform magnetic field perpendicular to the direction of motion of the particle. A charged particle moving perpendicular to a magnetic field will experience a centripetal force, causing it to move in a circular path. The radius of the circle is given by r=qB/mv, where m is the mass of the particle.
Explain how electric and magnetic fields can be used in velocity selection. Velocity selectors use both electric and magnetic fields to filter particles by velocity. Only particles with a specific velocity will have the electric force equal and opposite to the magnetic force, allowing them to pass through straight. The velocity that is selected is given by v=E/B, where E is the electric field strength.

1.

The formula F=BQvsinθ is used to calculate the magnitude of the force on the charge. Recall and use the formula F= (a) to calculate the magnitude of the force on the charge.

2.

How can electric and magnetic fields be used in velocity selection?

a)

To accelerate charged particles

b)

To deflect charged particles

c)

To filter charged particles

d)

To focus charged particles

3.

The use of a Hall probe to measure magnetic flux density, where the Hall voltage is directly proportional to the magnetic flux density is known as (a)

4.

What is the right-hand rule for positively charged particles and how is it used to determine the direction of the force?

4 lines

5.

What is the expression for Hall voltage?

a)

VH=BI/(ntq)

b)

VH=ntq/BI

c)

VH=IB/(ntq)

d)

VH=ntq/IB

6.

What is the motion of a charged particle in a uniform magnetic field perpendicular to its direction of motion?

a)

Circular motion

b)

Linear motion

c)

Oscillatory motion

d)

Spiral motion

7.

What is the direction of the force on a charge moving in a magnetic field?

4 lines

8.

What factors determine the strength of the magnetic field around a wire?

a)

Current and distance

b)

Voltage and resistance

c)

Temperature and pressure

d)

Mass and volume

9.

What is the force experienced by a charged particle in an electromagnetic field?

a)

Gravitational force

b)

Lorentz force

c)

Frictional force

d)

Tension force

10.

The Lorentz force is crucial in understanding the behavior of charged particles in various physical systems, such as particle accelerators and magnetic resonance imaging (MRI) machines.

(a)

11.

What is the equation for the Lorentz force?

a)

F = q(v x B)

b)

F = qvB

c)

F = qv/B

d)

F = q(v + B)

12.

What is the force experienced by a charged particle when it moves through a magnetic field?

4 lines

13.

A beam of electrons travels at 6.0×10⁶ m/s through a uniform magnetic field of 6.5×10⁻¹ T at right angles to the field. How strong is the force acting on each electron?

a)

= 6.25×10⁻¹³ N

b)

= −6.25×10⁻¹³ N

c)

= −6.25×10⁻¹⁰ N

d)

= −6.25×10⁻¹³ M

14.

Describe the path of a charge moving at right angles in a magnetic field

a)

straight (unchanged)

b)

parabola

c)

circular

d)

sinusoidal

15.

An electron is moving north in a region where the magnetic field is south. The magnetic force exerted on the electron is:

a)

zero

b)

up

c)

north

d)

south

16.

An electron and a proton are both initially moving with the same speed and in the same direction at 90˚ to the same uniform magnetic field. They experience magnetic forces, which are initially:

a)

identical

b)

equal in magnitude but opposite in direction

c)

in the same direction and differing in magnitude by a factor of 1840

d)

in opposite directions and differing in magnitude by a factor of 1840

17.

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

a)

I only

b)

II only

c)

III only

d)

II and III only

e)

I and IV only

18.

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 ______.

a)

zero because the velocity is perpendicular to the magnetic field

b)

300 m/s²toward the bottom of the page

c)

300 m/s²toward the top of the page

d)

600 m/s²toward the bottom of the page

e)

600 m/s²toward the top of the page

19.

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 ____.

a)

twice the original radius

b)

four times the original radius

c)

the same as the original radius

d)

one-half the original radius

e)

one-fourth the original radius

20.

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

a)

zero

b)

1.6 × 10^-21 𝑁

c)

3.2 × 10^-21 𝑁

d)

1.6 × 10^-20 𝑁

e)

3.2 × 10^-20 𝑁

21.

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°?

a)

2.0×10^-14 𝑁

b)

4.0×10^-14 𝑁

c)

2.0×10^-12 𝑁

d)

4.0×10^-12 𝑁

e)

6.0×10^-12 𝑁

22.

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?

a)

Now the particle travels in a clockwise circle of radius R

b)

Now the particle travels in a counterclockwise circle of radius R

c)

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

d)

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

e)

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

23.

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?

a)

b)

c)

d)

e)

24.

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?

a)

1 nm

b)

1 μm

c)

1 mm

d)

1 m

e)

1 km

25.

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

a)

I only

b)

II only

c)

III only

d)

II and III only

e)

I and IV only

26.

An electron is in a uniform magnetic field B that is directed out of the plane of the page, as shown above. When the electron is moving in the plane of the page in the direction indicated by the arrow, the force on the electron is directed

a)

toward the right

b)

out of the page

c)

into the page

d)

toward the top of the page

e)

toward the bottom of the page

27.

A particle of charge +Q moving with speed v₀ enters a region of constant magnetic field B directed into the page, as shown above. The initial direction and magnitude of the acceleration of the particle as it enters the magnetic field is toward the

a)

bottom of the page and proportional to B

b)

bottom of the page and proportional to v₀

c)

top of the page and inversely proportional to v₀

d)

top of the page and inversely proportional to B

e)

top of the page and proportional to both B and v₀

28.

A beam of protons moves parallel to the x-axis in the positive x-direction, as shown above, through a region of crossed electric and magnetic fields balanced for zero deflection of the beam. If the magnetic field is pointed in the positive y-direction, in what direction must the electric field be pointed?

a)

Positive y-direction

b)

Positive z-direction

c)

Negative x-direction

d)

Negative y-direction

e)

Negative z-direction

29.

As shown above, a positively charged particle moves to the right without deflection through a pair of charged plates. Between the plates are a uniform electric field E of magnitude 6.0 N/C and a uniform magnetic field B of magnitude 2.0 T, directed as shown in the figure. The speed of the particle is most nearly

a)

0.33 m/s

b)

0.66 m/s

c)

3.0 m/s

d)

12 m/s

e)

18 m/s

30.

A proton traveling with speed v enters a uniform electric field of magnitude E, directed parallel to the plane of the page, as shown in the figure above. There is also a magnetic force on the proton that is in the direction opposite to that of the electric force. If e represents the magnitude of the proton charge, what minimum magnitude of the magnetic field could balance the electric force on the proton?

a)

E/v

b)

eE/v

c)

vE

d)

eE

e)

evE

31.

A proton traveling with speed v enters a uniform electric field of magnitude E, directed parallel to the plane of the page, as shown in the figure above. There is also a magnetic force on the proton that is in the direction opposite to that of the electric force. Which of the following is a possible direction for the magnetic field?

a)

b)

c)

d)

e)

32.

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 ____:

a)

move in a straight line

b)

follow a spiral path

c)

move along a parabolic path

d)

move along a waveform

e)

follow a circular path

33.

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 ______.

a)

zero because the velocity is perpendicular to the magnetic field

b)

300 m/s²toward the bottom of the page

c)

300 m/s²toward the top of the page

d)

600 m/s²toward the bottom of the page

e)

600 m/s²toward the top of the page

34.

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 ____.

a)

twice the original radius

b)

four times the original radius

c)

the same as the original radius

d)

one-half the original radius

e)

one-fourth the original radius

35.

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°?

a)

2.0×10^-14 𝑁

b)

4.0×10^-14 𝑁

c)

2.0×10^-12 𝑁

d)

4.0×10^-12 𝑁

e)

6.0×10^-12 𝑁

36.

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?

a)

b)

c)

d)

e)

37.

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?

a)

All the particles are positively charges but have different mass

b)

All the particles have same mass, but different charges

c)

Two particles are positive while one is negative

d)

Two particles are negative while one is positive

e)

You can only ascertain that all are charged

Topic 20.3

Total questions: 26

Worksheet time: 49mins

Understanding Magnetic Fields and Charged Particles

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