Topic Introduction
Every electrical circuit contains voltage, current, power, and energy exchange. Network Analysis helps us understand how these quantities behave and interact inside the circuit.
In this chapter, charge is the basic quantity, when electric charge starts moving through a conductor, electrical current is produced. The amount of charge flowing every second determines how large the current is. Voltage is the potential difference between two points, power is the rate of energy transfer, and energy is the total work done by or on the circuit.
Key Idea / Intuition
Think of a circuit as a closed path with terminals, elements, and energy exchange. A source creates voltage, charges move as current, and elements either absorb, store, deliver, control, or restrict electrical energy.
Learning Goals
- Understand charge, current, voltage, power, and energy.
- Identify active, passive, linear, non-linear, bilateral, and unilateral elements.
- Use sign convention correctly before applying KCL, KVL, or Ohm's law.
Key Concepts
- Electric Charge, Current, and Voltage
- Power and Energy
- Passive and Active Elements
- Linear and Non-Linear Elements
- Bilateral and Unilateral Elements
Mathematical Definition
Keep the basic quantities close to their meaning. These formulas are useful only after voltage polarity and current direction are marked.
Current
I = dQ/dt
Current is the time rate of flow of charge.
Power
P = VI
Positive power means absorption under passive sign convention.
Energy
W = integral P dt
Energy is accumulated power over time.
Ohm's Law Preview
V = IR
This becomes useful after identifying voltage and current direction.
Visual Understanding
These normal circuit diagrams show how charge, current, voltage, power, and element behavior are marked before solving Network Analysis problems.
Voltage, current, and resistance
Mark the source polarity, current direction, and resistor voltage before writing equations.
Power and energy direction
The passive sign convention tells whether an element absorbs or delivers power.
Element behavior
Passive storage and direction-dependent behavior are easier to compare with circuit symbols.
Worked Example
Power direction check
A circuit element has marked voltage and current direction. Decide whether it absorbs or delivers energy before solving deeper network equations.
Important Notes
Exam Pointers
- Check whether the element is absorbing or delivering power.
- Keep conventional current direction separate from electron flow.
- Identify whether an element is active/passive, linear/non-linear, or bilateral/unilateral.
- Do not apply circuit laws before marking voltage polarity and current direction.
Exam-Oriented Tip
Most mistakes in Network Analysis begin before calculation: wrong polarity, wrong current direction, or wrong assumption about whether power is absorbed or delivered.
Quick Summary
Quick Revision Takeaway
- Voltage, current, power, and energy describe circuit behavior.
- Element type decides whether energy is absorbed, stored, delivered, controlled, or restricted.
- Mark polarity and current direction before applying laws or theorems.
Circuit Elements
Resistors, capacitors, inductors, Independent and dependent sources, Source transformation
Circuit Laws
Ohm's Law, Kirchhoff's Current Law (KCL), Kirchhoff's Voltage Law (KVL)
Network Theorems
Superposition Theorem, Thevenin's Theorem, Norton's Theorem
DC Circuit Analysis
Series and parallel circuits, Mesh analysis, Nodal analysis
AC Fundamentals
Sinusoidal signals, Phase and phasors, RMS, average values
AC Circuit Analysis
RL, RC, RLC circuits, Series and parallel resonance, Power in AC circuits: real, reactive, apparent