It is essential to know a few fundamental concepts, laws, electrical quantities, relationships and theorems for circuit analysis. Following are a few commonly used laws and circuit analysis techniques:
- Ohm’s law is an integral equation in network analysis that relates voltage, current and resistance.
- We make use of Kirchhoff’s laws to simplify a network of resistors into an equivalent resistor.
- For complicated circuits, we use node-voltage analysis and mesh current techniques.
- We use the Thévenin or Norton equivalent when we want to try different loads for a particular source circuit.
Three important laws to know while analyzing Circuits
Analyzing circuits at the basic level entails calculating current and voltage for a particular device. One of the important equations in network analysis, the Ohm’s Law, relates current and voltage using resistance.
The two important connection equations that one needs to know are Kirchhoff’s Voltage Law and Kirchhoff’s Current Law.
Kirchhoff’s Current Law, also known as the Kirchoff’s first law states that the current flowing into a node should be equal to the current flowing out it.
Kirchhoff’s Voltage Law, also known as the Kirchhoff’s second law states that the sum of all voltages around a closed circuit should be equal to zero.
Important Electric Quantities to Know
Certain electrical quantities are critical to know while analyzing circuit behaviour. Following we have listed a few of these important electric quantities:
Voltage (V) – Voltage is defined as pressure from an electrical circuit’s power source that pushes charged electrons through a conducting loop. Voltages are measured in a circuit by either using a voltmeter or a multimeter.
Current (I) – An electric current is defined as the rate of flow of electric charge past a point or a region. Current in a circuit is usually measured using an ammeter.
Power (W) – Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. Power in a circuit is measured using a wattmeter.
Resistance (R ) Resistance is defined as the property of an electric component to resist the flow of current. Resistance is measured in ohms. Resistors contain resistance colour code with colour bands that allow us to identify a resistor’s resistive value.
Capacitance (C ) – Capacitance is the ability of the system to store electric charges.
Inductance (L) – Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it.
Analysis Techniques for Complex Circuits
While dealing with complicated circuits with many loops and nodes, a few circuit analysis techniques come in handy. Following are a few of these techniques:
Node-Voltage Analysis – In a node-voltage analysis, the unknown voltage is identified using Kirchhoff’s current law. Once the node voltage is determined, we make use of Ohm’s law to find device currents and use node voltage to find device voltages.
Superposition Theorem – Superposition theorem is used to find the voltages and current output of a particular device in linear circuits with independent sources. In this method, only one source is considered at a time. We can negate current sources by replacing them with an open circuit; likewise, we can turn off the voltage source by replacing it with a short circuit. The total output is obtained by calculating the algebraic sum of individual contributions of each source.
Mesh Current Analysis – In this type of analysis, mesh currents in a circuit are determined in a circuit using Kirchhoff’s voltage law. Mesh equations are KVL equations with unknown mesh currents as variables.