PH 122 Lecture Notes - Relative Permittivity, Exponential Decay, Farad
Document Summary
Charge on a capacitor with potential difference vc. Unit: farad, f; 1 farad = 1 f = 1 c/v. Capacitance of a parallel-plate capacitor with plate area a, separation d. Capacitance of a parallel-plate capacitor with a dielectric of dielectric constant . Ceq = c1 + c2 + c3 + + cn. Exponential decay occurs when a quantity y is proportional to the number e taken to the power t/ . The quantity is known as the time constant. Whenever t increases by one time constant, y decreases by a factor of 1/e. At time t = 0, y = a. Increasing time to t = reduces y to a/e. A further increase to t = 2 reduces y by another factor to 1/e to a/e2. At t = n , y has the value a/en. As t becomes large, y becomes very small and approaches zero.
