Applied Electricity Lecture Notes

CHAPTER 1: CIRCUIT LAWS

1.1 Introduction
Applied electricity focuses on the practical application of electrical principles, involving the flow of charge and the behavior of components in electrical systems.
1.3 Ohm’s Law
States that the current I flowing through a conductor is directly proportional to the voltage V across it, provided the temperature remains constant.

• Formula: V = I \cdot R
• R is the resistance measured in Ohms (\Omega).
  1.4 Kirchhoff’s Voltage Law (KVL)
  The algebraic sum of all voltages around any closed loop in a circuit is zero.
• \sum V = 0
  1.5 Kirchhoff’s Current Law (KCL)
  The total current entering a node is equal to the total current leaving that node.
• \sum I{in} = \sum I{out}
  1.11 Electrical Power and Energy
• Electrical Power (P): The rate at which work is done or energy is transferred. P = V \cdot I = I^2 \cdot R = \frac{V^2}{R}. Measured in Watts (W).
• Electrical Energy (E): The total work done over time. E = P \cdot t. Measured in Joules (J) or kilowatt-hours (kWh).

CHAPTER 2: CIRCUIT THEOREMS

2.4 Superposition Theorem
In a linear circuit with multiple independent sources, the response (voltage or current) in any branch is the sum of the responses caused by each source acting alone, while all other independent sources are replaced by their internal impedances (voltage sources shorted, current sources opened).
2.5 Thévenin’s Theorem
States that any linear, bilateral network can be replaced by an equivalent circuit consisting of a single voltage source V{th} in series with a resistor R{th}.
2.8 Maximum Power Transfer Theorem
Maximum power is transferred from a source to a load when the load resistance RL is equal to the Thévenin resistance R{th} of the source (RL = R{th}).

CHAPTER 3: CAPACITORS AND CAPACITANCE

3.3 Capacitance (C)
The ability of a system to store electric charge (Q) per unit of potential difference (V).

• Formula: C = \frac{Q}{V}
• Measured in Farads (F).
  3.7 The Parallel Plate Capacitor
  Capacitance is determined by the area of the plates (A), the distance between them (d), and the permittivity (\epsilon) of the dielectric material.
• C = \epsilon \cdot \frac{A}{d}
  3.10 Energy Stored
  The energy stored in a capacitor is given by:
• W = \frac{1}{2} C V^2

CHAPTER 4: MAGNETIC CIRCUITS

4.2 Magnetic Flux (\Phi) and Flux Density (B)

• Flux (\Phi): Total magnetic field lines passing through a surface, measured in Webers (Wb).
• Flux Density (B): Flux per unit area. B = \frac{\Phi}{A}. Measured in Teslas (T).
  4.3 Magnetomotive Force (MMF)
  The "driving force" that produced magnetic flux.
• MMF = N \cdot I, where N is the number of turns and I is current.
  4.5 Reluctance (S)
  The opposition to the magnetic flux, analogous to resistance in an electric circuit.
• S = \frac{l}{\mu A}, where l is length and \mu is permeability.