Define the term magnetic flux density.
Electrons move in a vacuum with speed $1.7 \times 10^{7} \, \text{m s}^{-1}$. They enter a uniform magnetic field with flux density $4.8 \, \text{mT}$. Fig. 6.1 shows the route taken by the electrons. Their path stays in the plane of the page. State the direction of the magnetic field.
Show that the size of the force on each electron due to the magnetic field is $1.3 \times 10^{-14} \, \text{N}$.
On Fig. 6.1, draw an arrow to show the direction of the centripetal acceleration of the electron as it enters the magnetic field at point X.
Use the information in (b)(ii) to calculate the distance $d$ between the path of the electrons entering the magnetic field and the path of the electrons leaving it.
The electrons in (b) are replaced by positrons that move with speed $3.4 \times 10^{7} \, \text{m s}^{-1}$ along the same initial path as the electrons. The positrons enter the magnetic field at point X on Fig. 6.1. On Fig. 6.1, draw a line to show the path of the positrons through the magnetic field.