# Calculating Charge and Time in a Discharging RC Circuit

• Moolisa
In summary, the conversation discusses an RC circuit with a resistor, capacitor, and switch, where the switch is initially open and closed at t=0. The charge in the capacitor is determined by using the formula ΔVC=Q/C, and the current is 33μA. The solution also considers the use of Q=Q0 e-t/RC to find the time, but the computation of Q0 is not shown and clarification is needed.
Moolisa

## Homework Statement

RC circuit, with a resistor, capacitor and a switch with
ΔVC =80V R=1.5MΩ C=22μF
The switch is initially open. The switch is closed at t=0
(a) What is the charge in the capacitor when the current is 33μA
(b) How times does it take for the current to reach 33μA
2. The attempt at a solution
(a) So I think the capacitor is discharching.
Since ΔVC -IR=0, and ΔVC=Q/C is the charge when I=33μA
Q=IRC?
(b) If part (a) is correct, can I use Q=Q0 e-t/RC and find the time from there?

It looks correct to me. For part b, how do you compute ## Q_o ##? I don't think you showed that.

Moolisa
It looks correct to me. For part b, how do you compute ## Q_o ##? I don't think you showed that.
Is it C(80V)?

I'd like to see the circuit.

## What is an RC circuit?

An RC circuit is an electronic circuit that contains a resistor (R) and a capacitor (C) connected in series or parallel. It is used in many applications, including filters, oscillators, and timers.

## How does an RC circuit discharge?

An RC circuit discharges when the capacitor releases its stored energy through the resistor. This process is known as the discharge curve, and it follows an exponential decay pattern.

## What factors affect the discharge time of an RC circuit?

The discharge time of an RC circuit is affected by the resistance and capacitance values in the circuit. A higher resistance or capacitance will result in a longer discharge time, while a lower resistance or capacitance will result in a shorter discharge time.

## What is the equation for calculating the discharge time of an RC circuit?

The equation for calculating the discharge time of an RC circuit is t = RC, where t is the time in seconds, R is the resistance in ohms, and C is the capacitance in farads.

## What are some practical applications of discharging an RC circuit?

Discharging an RC circuit is commonly used in electronic devices such as flashlights, camera flashes, and defibrillators. It is also important in creating smooth voltage transitions in power supplies and audio equipment.

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