This diagram shows the structure of a spark plug in an internal combustion engine. The magnified section shows the end of the spark plug, with some of the lines of force representing the electric field.
What evidence does the diagram give that the field is strongest near the tip of the inner electrode?
Important Questions on Uniform Electric Fields
The gap between the inner and outer electrodes is $1.25 \mathrm{~mm}$ and a field strength of $5.0 \times 10^{6} \mathrm{NC}^{-1}$ is required for electrical breakdown. Estimate the minimum potential difference that must be applied across the inner and outer electrodes for a spark to be produced. (You may treat the two electrodes as a pair of parallel plates.)
The gap between the inner and outer electrodes is $1.25 \mathrm{~mm}$ and a field strength of $5.0 \times 10^{6} \mathrm{NC}^{-1}$ is required for electrical breakdown. When an electron is accelerated through a potential drop of approximately $20 \mathrm{~V}$ it will have sufficient energy to ionise a nitrogen atom. Show that an electron must move $4.0 \mu \mathrm{m}$ to gain this energy.
