Solving a problem in physics section 1 paragraph 16 ele

16. planar air condenser plates a potential difference of 1.5 kV. Area 150 cm2 plates and spacing of 5 mm. After disconnecting the capacitor from the voltage source to the space between the glass plates made (ε2 = 7). To determine: 1) the potential difference between the plates of U2 after making the dielectric; 2) the capacitance of the capacitor C1 and C2 until after making the dielectric; 3) the surface charge density on the plates to σ1 and σ2 after making the dielectric.