Lecture Notes: Resistance, Reactance, and Impedance

Introduction

Voltage Difference:
- If voltage at both ends (A and B) is equal, no current flows (light bulb off).
- Current flows from B to A if voltage at B exceeds that of A, and vice versa.
Types of Current:
- Direct Current (DC): Voltage remains constant, resulting in constant current.
- Alternating Current (AC): Voltage varies, causing current to change in magnitude and direction frequently.

Graphs of voltage and current:
- DC Circuit: Constant voltage and current.
- AC Circuit: Voltage varies in a sine wave pattern, current follows the same pattern.

Types of Changes:
1. Decrease in Magnitude: Observed in both AC and DC circuits.
2. Delayed Current Change: Occurs in AC circuits after voltage change.
3. Leading Current Change: Current changes before voltage change, exclusive to AC circuits.
Types of current change:
- First type = Resistance
- Second and third types = Reactance (Inductive and Capacitive)
  - Inductive Reactance: Current lags behind voltage.
  - Capacitive Reactance: Current leads voltage.

Components: Resistors, inductors, and capacitors.
Water Analogy:
- Flow in Pipes:
  - High pressure (voltage) causes water (current) to flow from high to low.
  - Resistors decrease flow (current) like a narrow nozzle.
Inductors:
- Delay changes in current, compared to a water wheel.
- Not influential in DC; evident in AC.
Capacitors:
- Delay changes in force (voltage), compared to an elastic membrane.
- Current leads voltage in AC, not evident in DC.

Resistance:
- Always decreases current, observable in both AC and DC.
Inductive Reactance:
- Causes lag in current relative to voltage, only in AC.
Capacitive Reactance:
- Causes current to lead voltage, only in AC.
Impedance:
- Cumulative effect of resistance, inductive reactance, and capacitive reactance on current in a circuit.