State Coulomb’s law in words.
In a vacuum, two identical oil droplets have centres separated by $3.8 \times 10^{-6}\,\text{m}$. Their charges are equal, and the electric force each exerts on the other has magnitude $6.3 \times 10^{-17}\,\text{N}$. Determine the magnitude of the charge on each droplet.
In part (b), one of the oil droplets is now placed between two horizontal metal plates, as shown in Fig. 5.1. A potential difference (p.d.) of $1200\,\text{V}$ is applied across the plates, with the top plate at the higher potential. The oil droplet remains stationary in equilibrium. State the sign of the charge on the oil droplet.
On Fig. 5.1, draw four lines to show the electric field between the plates.
The plate separation is $5.2\,\text{cm}$. Determine the mass of the oil droplet.
State the sign of the charge on the oil droplet.
On Fig. 5.1, draw four lines to show the electric field between the plates.
The plate separation is $5.2\,\text{cm}$. Determine the mass of the oil droplet.