Define what is meant by the coulomb.
Two vertical metal plates in a vacuum are separated by $4.0\,\text{cm}$. A potential difference of $2.0 \times 10^{2}\,\text{V}$ is applied across the plates. Fig. 5.1 gives a side view of the setup. A smoke particle lies in the uniform electric field between the plates. Its weight is $3.9 \times 10^{-15}\,\text{N}$ and its charge is $-8.0 \times 10^{-19}\,\text{C}$.
Show that the electric force on the particle has magnitude $4.0 \times 10^{-15}\,\text{N}$.
On Fig. 5.1, add labelled arrows to indicate the directions of the two forces acting on the smoke particle.
The particle experiences a resultant force $F$. Find the magnitude of $F$.
Find the angle that $F$ makes with the horizontal.
The electric field in (b) is switched on at time $t = 0$ when the particle is at a horizontal displacement $s = 2.0\,\text{cm}$ from the left-hand plate. At time $t = 0$ the horizontal velocity of the particle is zero. The particle is then moved by the electric field until it hits a plate at time $t = T$. On Fig. 5.2, sketch the variation with time $t$ of the horizontal displacement $s$ of the particle from the left-hand plate.
The resultant force on the particle is $F$. Determine 1. the magnitude of $F$, 2. the angle of $F$ to the horizontal.