Lecture Notes: Inductors

Definition

• An inductor is a coil of wire wrapped around a magnetic material.
• It creates a magnetic field when current flows through it.
• Inductors resist changes in the current flowing through them.

Behavior of Inductors

• Constant Current:
  • Acts like a normal wire when current is constant.
  • No forces are generated on charged particles.
• Changing Current:
  • Generates a force to prevent change in current.
  • If interrupted, tries to maintain current flow.

Circuit Dynamics

• Connected Inductor:
  • With no resistance, current could circulate indefinitely (theoretically).
  • In reality, resistance causes the current to decay to zero.
  • Resistance vs. Inductance:
    • Larger resistance = faster current decay.
    • Larger inductance = slower current decay.
• Zero Current:
  • Inductor maintains zero current once reached.

Inductor in a Circuit

• Initial Connection:
  • Resists increase in current.
  • Larger inductance slows current increase.
• Steady-State Current:
  • No forces are generated when current is steady.
  • Upon switching off, tries to maintain current at new constant value.

Resistor-Inductor Interaction

• Voltage Across Resistor:
  • Voltage = Current x Resistance.
  • Inductor prevents instantaneous change in current.

High Voltage Generation

• Resistor with Large Value:
  • Can generate extremely high voltages, briefly.
• Path for Current:
  • Essential to provide a path when disconnecting inductor.
  • Without a path, current may find unintended paths (e.g., through air or components), causing damage.

Applications and Cautions

• Power Supply Design:
  • Inductors useful due to ability to create large voltages.
• Safety Precautions:
  • Ensure a current path when switching off to prevent damage.

Further Learning

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