RC Circuits

🔖 Topics

• Simple RC circuits

🎯 Objectives

• Calculate the charge on a capacitor as a function of time in a simple charging RC circuit
• Calculate the charge on a capacitor as a function of time in a simple discharging RC circuit
• Calculate the current and current as functions of time in a simple charging RC circuit
• Calculate the current and current as functions of time in a simple discharging RC circuit

📋 Sequence

• 🟢 Overview of RC circuits
• 🟢 Derivation of the equations that govern simple RC circuits
• 🟢 Time constants
• 🟣 Charging circuits
• 🟣 Discharging circuits

🖥️ Animations, Simulations, Activities

• RC Circuit from the Circuit Lab

📝 Practice Problems

1. A capacitor of $0.10\mu F$ is charged to 90 V and then connected to a $30k\Omega$ resistor. What will the voltage across the resistor be after 8.4 ms?
2. A capacitor of $0.050\mu F$ is initially uncharged and connected in series to a 12 V battery and a $40k\Omega$ resistor. What is the current in the circuit at time t = 0 seconds? What is the current in the circuit at time t = 1 second?
3. In a charging RC circuit, how many time constants have elapsed when the capacitor has 99% of its final charge?

✅ Partial Solutions

1. 5.5 V
2. 0.30 mA; 0.18 mA
3. 4.6 time constants

📘 Connected Resources

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