## RC Circuits

6.5 RC Circuits

### Learning Objectives

By the end of this section, you will be able to:

- Describe the charging process of a capacitor
- Describe the discharging process of a capacitor
- List some applications of RC circuits

### RC Circuits

An *RC* circuit is one containing a resistor *R* and a capacitor *C*. The capacitor is an electrical component that stores electric charge and electric energy.

Here is an example of an RC circuit

In this circuit we have a battery that provides an emf, a switch that allows us to close the circuit and charge the capacitor, a capacitor and a resistor in series. Let’s assume the capacitor is not charged yet. When we close the switch, then the battery will move charge from one capacitor plate to the other and that moving charge (current) will flow through the resistor.

What is the time constant of the circuit shown in the figure below? Each of the five resistors has resistance R, and each of the five capacitors has capacitance C. The internal resistance of the battery is negligible.

**Practice!**

Practice 6.5.1 |
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The two circuits shown contain identical fully charged capacitors at t = 0. Circuit 2 has twice as much resistance as circuit 1. Compare the charge on the two capacitors a short time after t = 0. |

Practice 6.5.2 |
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Consider the circuit shown in the figure and assume the battery has no internal resistance. Just after the switch is closed, what is the current that flows through the battery? |

Practice 6.5.3 |
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Consider the circuit shown in the figure and assume the battery has no internal resistance. A very long time after the switch has been closed, what is the current that flows through the battery? |