IB Physics D.3 Motion in Electromagnetic Fields Questionbank

(d) Calculate the speed of an electron accelerated from rest through a potential difference of 4.0 kV.

(e) Determine the radius of the circular path taken by the electron in a magnetic field of 0.30 T.

(f) Suggest why a vacuum is necessary in the tube containing the electron beam.

In a laboratory experiment, singly ionized calcium ions (Ca⁺) of mass $6.66 \times 10^{-26}\ \text{kg}$ and charge $1.60 \times 10^{-19}\ \text{C}$ are accelerated through a potential difference of 5.0 kV before entering a uniform magnetic field of strength $0.45\ \text{T}$. The magnetic field is perpendicular to the velocity of the ions.

(a) Calculate the final speed of the calcium ions after acceleration.

(b) Determine the radius of the path followed by the ions in the magnetic field.

(d) Suggest why mass spectrometers must be operated under low-pressure conditions.

A wire of length $0.50\ \mathrm{m}$ carries a current of $3.0\ \mathrm{A}$ perpendicular to a uniform magnetic field of $0.40\ \mathrm{T}$. If the wire is suspended horizontally and remains motionless, what is the minimum mass that the wire must have per unit length?

A charged particle moves at speed $v$ in a uniform magnetic field $B$, entering at an angle $\theta$ to the field direction. What is the shape of its trajectory?

A beam of electrons travels in a region with perpendicular electric and magnetic fields. The electric field is $200\ \mathrm{V\ m}^{-1}$ and the magnetic field is $0.50\ \mathrm{mT}$. What is the speed of the electrons if they move undeflected?

(c) Describe the path taken by the electron in the magnetic field and explain the cause of this motion.

(c) Explain the effect on the radius if the same field is used with doubly ionized calcium ions ($\text{Ca}^{2+}$).