Answer to Question #112377 in Electric Circuits for Brittney

Question

Explain what happens to the potential difference across a discharging capacitor after three (3) time constants have elapsed. (3 marks)

Answer 1

Formula for potential difference as a function of time if given by

$$V_c=V_s\times e^{\frac{-t}{RC}}$$

• $V_c$  is the voltage across the capacitor
• $V_s$ is the supply voltage
• $t$  is the elapsed time since the removal of the supply voltage
• $RC$  is the time constant of the RC discharging circuit

So here t= 3RC

putting the value

We get,

$$V_c= V_s\times e^{-3}$$

So after this time it will reduced $\frac{1}{e^3}$ of its original value.