Conservation of Energy in a Circuit?

📌 CONCEPT: In an LCR series circuit, energy is conserved in the form of electrical energy when the circuit is connected to a power source and in the form of potential and kinetic energy when the components are isolated and free to oscillate.

📐 RULE / FORMULA: According to the law of conservation of energy, the total energy remains constant in an isolated system, which in this case is the LCR series circuit.

💡 WORKED EXAMPLE: Consider a circuit with an inductor (L = 10 mH), a capacitor (C = 10 μF), and a resistor (R = 10 Ω). When the circuit is connected to a power source, the electrical energy is converted into heat energy in the resistor and into potential and kinetic energy in the inductor and capacitor. When the circuit is disconnected, the potential and kinetic energy stored in the inductor and capacitor is converted into heat energy through friction.

⚠️ COMMON MISTAKE: Students often confuse the concept of energy conservation with the concept of energy conversion, assuming that energy is lost or gained in the circuit when in fact it is conserved in the form of different types of energy.