1. The problem statement, all variables and given/known data A multi plate variable capacitor has 4 pair of plates. The plates, when closed, are separated in air by 0.01mm and a capacitance range of 10 to 400pF. a) Estimate the required radius R of each plate. b) The capacitor is set to maximum 400pF and is charged to 10V through a 50kΩ resistor. Determine: i) The initial value of the current flowing. ii) The time constant for the circuit. 2. Relevant equations C = εr εo A (n-1)/d 3. The attempt at a solution I am still new to all this so please dont go too technical with any replies. I think the correct formula to work out the radius is C=εr εo A (n-1)/d Transpose this to make A the subject: A= Cd/εr εo (n-1) Which gives me A= (400x10^-12)x(0.00001)/1 x 8.85x10^-12 x 7 Area of plate = 0.00316 (I think this is meter^2) Then use this answer in A=∏r^2 Transpose for radius = √A/∏ Which gives me an answer of 0.0317 (Again I think this is meters). bi) The initial value of current flowing. If t=0 The charging current has its highest value. Therefore io=V/R =10/50000 =0.0002 Amps bii) The time constant t=CR t=(400x10^-12)x 50000 t=0.00002s Could you tell me if I am going about these the correct way or am I way off mark thanks.