The Quasistationary Approximation Ampere’s Law + Faraday’s Law Application in: electrical engineering, radio, TV, audio, … time x velocity of light >> size

Inductance inductive coupling between two circuits

Example 7.10 Find the mutual inductance.

Mutual inductance?

Self-inductance The change of B induces a back-emf in the loop that generates the magnetic field: self-induction. L self-inductance Unit: Henry 1H=1Vs/A

Example 7.11 Self-inductance of a toroidal coil with recangular cross section, which carries a total of N turns.

The transformer

Low current and high voltage used. Long distant line Distribution within a neighborhood

Example 7.12

Oscillator Circuits C

Driven Oscillator C AC

Driven oscillator with different initial conditions.

Resonance

Self-excited circuit Radio tubes 1930

A shipboard radio, circa Exposed at the operator’s left are the inductance coils and capacitor plates of the tuning circuit.

transistors microchip

Multi-loop Circuits Kirchhoff’s rules: 1.When any closed-circuit loop is traversed, the algebraic sum of the changes in the potential must be equal to zero. 2. At any junction point in a circuit where the current can divide, the sum of the currents into the junction must equal the sum of the currents out of the junction.

DC circuit Find the currents.

AC circuit