In an RC circuit, what fraction of the final energy is stored in an initially uncharged capacitor after it has been charging for 3.0 time constants?
A) 0.84
B) 0.90
C) 0.75
D) 0.60
E) 0.03

Question

Quizplus · Accepted Answer

After 3 time constants (3RC), the capacitor will be charged to approximately 95% of its final energy. The equation for the energy stored in a capacitor is E = 1/2 * C * V^2, where C is the capacitance and V is the voltage across the capacitor. The time constant for an RC circuit is given by the equation tau = RC. After 3 time constants, the capacitor will have charged to approximately 1 - (1/e)^3 = 0.95 of its final energy. Therefore, the fraction of the final energy stored in the capacitor after 3 time constants is approximately 0.95^2 = 0.9025, which is closest to choice B (0.90).

In an RC Circuit, What Fraction of the Final Energy