A 0.350-{\rm m}-long cylindrical capacitor consists of a solid conducting core with a radius of 1.25mm and an outer hollow conducting tube with an inner radius of 2.10mm . The two conductors are separated by air and charged to a potential difference of 6.10V .
1- Calculate the charge per length for the capacitor.
2- Calculate the total charge on the capacitor.
3- Calculate the capacitance.
4- Calculate the energy stored in the capacitor when fully charged.