1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution 1) "One plate is maintained at +75 V while the other at -75 V by a d.c. supply" means? Does it means that this capacitor is connected to a 150 V d.c. supply or just a 75 V? 2) Why is 75-(-75)? Why don't we just use 75V? 3) Charge stored on each plate is it the same as charge stored in the whole capacitor?