Thevenin and Norton equivalents
Thevenin and Norton equivalents are simplified representations of complex electrical circuits. Thevenin’s theorem states that any linear circuit can be reduced to a single voltage source in series with a resistor. Norton’s theorem offers a parallel form, using a current source in parallel with a resistor. These equivalents make circuit analysis easier, especially for calculating current or voltage across specific components, by focusing on terminal behavior rather than internal complexity.
Thevenin and Norton equivalents
Thevenin and Norton equivalents are simplified representations of complex electrical circuits. Thevenin’s theorem states that any linear circuit can be reduced to a single voltage source in series with a resistor. Norton’s theorem offers a parallel form, using a current source in parallel with a resistor. These equivalents make circuit analysis easier, especially for calculating current or voltage across specific components, by focusing on terminal behavior rather than internal complexity.
💡 Key Takeaways
- Learn Thevenin's and Norton's theorems and what they replace in a circuit.
- Convert a linear network into a Thevenin equivalent: a voltage source in series with Rth.
- Convert the same network into a Norton equivalent: a current source in parallel with Rth.
- Use the relationships between the two: Vth = In × Rth and In = Vth / Rth; Rth is the same for both.
- Practice finding Thevenin/Norton equivalents by deactivating independent sources and simplifying resistors to determine Vth, In, and Rth for a given pair of terminals.
❓ Frequently Asked Questions
What is a Thevenin equivalent circuit?
A Thevenin equivalent represents a linear network as a single voltage source Vth in series with a resistance Rth, as seen from the output terminals.
What is a Norton equivalent circuit?
A Norton equivalent represents the same network as a current source In in parallel with the same Rth, seen from the output terminals.
How do you convert between Thevenin and Norton equivalents?
Rth stays the same. Vth = In × Rth, and In = Vth / Rth.
How do you find Thevenin resistance and the open/short-circuit values?
Find Voc (open-circuit voltage) and Isc (short-circuit current). Then Rth = Voc / Isc. To compute Rth directly, deactivate independent sources (voltage sources shorted, current sources opened); for circuits with dependent sources, use a test source to determine Rth.