Question:
Two discharge tubes have identical material structure and the same gas is filled in them. The length of one tube is $10 \mathrm{~cm}$ and that of the other tube is $20 \mathrm{~cm}$. Sparking starts in both the tubes when the potential difference between the cathode and anode is $100 \mathrm{~V}$. If the pressure in the shorter tube is $1.0 \mathrm{~mm}$ of mercury, what is the pressure in the longer tube?
Solution:
