Worksheet: Electron Beams

In this worksheet, we will practice calculating the electrical properties of electron beams and describing the uses of electron beams in imaging.

Q1:

A beam of neutrons in a vacuum is passed between two charged metal plates. Which of the following diagrams shows the trajectory that the neutron beam will follow when it passes between the plates? The red plate is the positively charged plate, and the blue plate is the negatively charged plate. Ignore the effect of gravity.

  • A
  • B
  • C
  • D

Q2:

An electron beam in a vacuum is passed between two charged metal plates. Which of the following shows the trajectory that the electron beam will follow when it passes between the plates? The red plate is the positively charged plate, and the blue plate is the negatively charged plate. Ignore the effect of gravity.

  • A
  • B
  • C
  • D

Q3:

In an electron beam, 1 . 2 5 × 1 0 electrons pass a point 𝑃 in 1 second. What is the current of the beam? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

Q4:

Which of the following is the correct formula for the current, 𝐼 , of a beam of charged particles given the number of particles passing a point, the charge on each particle 𝑞 , and the time it takes for the particles to pass the point?

  • A 𝐼 = 𝑞 ( 𝑛 𝑡 )
  • B 𝐼 = 𝑛 ( 𝑞 𝑡 )
  • C 𝐼 = 𝑛 𝑞 𝑡
  • D 𝐼 = 𝑛 𝑞 𝑡
  • E 𝐼 = 1 ( 𝑛 𝑞 𝑡 )

Q5:

An electron in a vacuum is accelerated across a potential difference of 3 V. What is the kinetic energy of the electron once it has crossed this potential difference? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

  • A 1 . 8 6 × 1 0 J
  • B 5 . 3 3 × 1 0 J
  • C 7 . 2 × 1 0 J
  • D 4 . 8 × 1 0 J
  • E 4 . 6 × 1 0 J

Q6:

An electron beam has a current of 0.02 A. How long does it take for 2 . 5 × 1 0 electrons to pass a point 𝑃 in the beam? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

Q7:

An electron beam has a current of 0.01 A. How many electrons pass a point 𝑃 in the beam every second? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

  • A 1 2 . 5 × 1 0
  • B 3 . 1 2 5 × 1 0
  • C 1 . 6 × 1 0
  • D 6 . 2 5 × 1 0
  • E 1 . 6 × 1 0

Q8:

Which of the following is the correct formula for the kinetic energy of a charged particle, with a charge 𝑞 , that has been accelerated across a potential difference, 𝑉 ?

  • A 𝐸 = 𝑉 𝑞
  • B 𝐸 = 𝑞 𝑉
  • C 𝐸 = 1 2 𝑞 𝑉
  • D 𝐸 = 𝑞 𝑉
  • E 𝐸 = 𝑞 + 𝑉

Q9:

An electron is accelerated between two charged parallel plates. The plates are 1.5 cm apart, and the potential difference between them is 1 2 V. The electron starts at the negative plate and accelerates toward the positive plate. The space between the plates is a vacuum.

What is the kinetic energy of the electron just before it hits the positive plate? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

  • A 1 3 . 6 × 1 0 J
  • B 9 . 6 × 1 0 J
  • C 1 . 5 4 × 1 0 J
  • D 1 . 9 2 × 1 0 J
  • E 1 . 1 5 × 1 0 J

What is the average force experienced by the electron as it moves between the plates?

  • A 1 . 2 8 × 1 0 N
  • B 1 . 2 8 × 1 0 N
  • C 1 . 2 8 × 1 0 N
  • D 1 . 2 8 × 1 0 N
  • E 2 . 8 8 × 1 0 N

Q10:

An electron passes into a uniform electric field. Before entering the field, the velocity of the electron is perpendicular to the magnetic field. Which of the following diagrams shows the trajectory that the electron takes when it enters the uniform magnetic field?

  • A
  • B
  • C
  • D

Q11:

An electron in a vacuum is accelerated across a potential difference of 8 V. The charge of an electron is 1 . 6 × 1 0 C, and an electron has a mass of 9 . 1 × 1 0 kg. What is the speed of the electron once it has crossed the potential difference?

  • A 1 . 2 × 1 0 m/s
  • B 2 . 8 × 1 0 m/s
  • C 8 . 4 × 1 0 m/s
  • D 1 . 7 × 1 0 m/s
  • E 4 . 7 × 1 0 m/s

Q12:

A beam of alpha particles in a vacuum is passed between two charged metal plates. Which of the following diagrams shows the trajectory that the alpha particles will follow when they pass between the plates? The red plate is the positively charged plate, and the blue plate is the negatively charged plate. Ignore the effect of gravity.

  • A
  • B
  • C
  • D

Q13:

A beam of positrons in a vacuum is passed between two charged metal plates. Which of the following shows the trajectory that the positron beam will follow when it passes between the plates? The red plate is the positively charged plate, and the blue plate is the negatively charged plate. Ignore the effect of gravity.

  • A
  • B
  • C
  • D

Q14:

What is the kinetic energy of an electron that is accelerated across a potential difference of 1 V? Assume that the electron moves in a vacuum. Use a value of 1 . 6 × 1 0 C for the charge of the electron.

  • A 2 . 6 × 1 0 J
  • B 6 . 2 5 × 1 0 J
  • C 8 × 1 0 J
  • D 1 . 6 × 1 0 J
  • E 6 . 1 × 1 0 J

Q15:

An electron in vacuum is accelerated across a potential difference. Once it has crossed this potential difference, its kinetic energy is found to be 8 × 1 0 J. What potential difference was the electron accelerated across? Use a value of 1 . 6 × 1 0 C for the charge of an electron.

Q16:

A block of an unknown material emits charged particles. These particles are accelerated in a vacuum across an electric potential difference of 6 V. The kinetic energy of each particle is found to be 1 . 9 2 × 1 0 J once it has crossed this potential difference.

What is the charge of each particle?

  • A 1 . 6 × 1 0 C
  • B 3 . 2 × 1 0 C
  • C 1 . 6 × 1 0 C
  • D 3 . 2 × 1 0 C
  • E 1 . 1 5 × 1 0 C

Using a value of 1 . 6 × 1 0 C for the charge of a proton, what is the relative charge of each particle?

It is found that the charged particles are being emitted by radioactive decay of the material in the block. What kind of particles are being emitted by the block?

  • ANeutrons
  • B 𝛽 particles
  • C 𝛼 particles
  • D 𝛾 rays
  • EX-rays

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