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Lesson: Motion of a Charged Particle in Combined Electric and Magnetic Fields

Sample Question Videos

Worksheet • 9 Questions • 1 Video

Q1:

A velocity selector uses both a magnetic field of magnitude 0.051 T and an electric field of magnitude 2 . 2 × 1 0 5 V/m.

At what speed must a proton move in the selector to pass through it undeflected?

  • A 4 . 3 × 1 0 6 m/s
  • B 6 . 7 × 1 0 6 m/s
  • C 2 . 1 × 1 0 6 m/s
  • D 5 . 0 × 1 0 6 m/s
  • E 9 . 6 × 1 0 6 m/s

At what speed must an alpha particle move in the selector to pass through it undeflected?

  • A 4 . 3 × 1 0 6 m/s
  • B 2 . 1 × 1 0 6 m/s
  • C 5 . 0 × 1 0 6 m/s
  • D 9 . 6 × 1 0 6 m/s
  • E 6 . 7 × 1 0 6 m/s

At what speed must a singly ionized 𝑂 1 6 atom move in the selector to pass through it undeflected?

  • A 4 . 3 × 1 0 6 m/s
  • B 6 . 7 × 1 0 6 m/s
  • C 5 . 0 × 1 0 6 m/s
  • D 9 . 6 × 1 0 6 m/s
  • E 2 . 1 × 1 0 6 m/s

Q2:

An electron in the cathode-ray tube of an old television moves at a speed of 5 . 6 × 1 0 7 m/s in a direction perpendicular to Earth’s magnetic field, which has a magnitude of 5 . 0 × 1 0 5 T in the region around the electron. Usually, televisions that use cathode-ray tubes are magnetically shielded so that electrons inside the tubes are not deflected by Earth’s magnetic field, but this television is not shielded. Instead, an electric field is applied perpendicular to the direction of Earth’s magnetic field and perpendicular to the direction of the electron’s velocity, which results in the electron moving in a straight line.

What is the magnitude of the applied electric field?

The applied electric field is produced between parallel plates separated by a 1.00 cm distance. What is the potential difference across the plates?

Q3:

A particle of charge 1 . 6 × 1 0 1 9 C and mass 1 . 6 7 × 1 0 2 5 kg is accelerated from rest through a potential difference of 8.2 kV. The particle then enters a uniform magnetic field of strength 0.47 T, moving in a plane perpendicular to the direction of the field. What is the radius of the particle’s circular orbit in the magnetic field?

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