Magnetic Fields Gausss Law vs Amperes Law Amperes

Magnetic Fields • Gauss’s Law vs. Ampere’s Law • Ampere’s Law for long straight wire • Examples • Magnetic properties of materials • Force between 2 parallel wires • Motors • Loudspeakers

Magnetism and Induction Flowchart law change field Current force direct examples Force Law 1 B → qv → F = qv x B RHR 1 charge deflection picture tube Force Law 2 B → il → F = il x B RHR 1 2 wires, motor, loudspeaker RHR 2 electromagnet solenoid Lentz generator transformer Ampere’s Law Faraday Induction B = μoi/2πr d/dt → ← i Φ = B*A → ε = dΦ/dt i = ε/R Current creates magnetic field

Gauss’s vs. Ampere’s Law • Gauss’s Law for closed surface – Flux lines penetrating closed surface equals charge enclosed. • Ampere’s Law for closed loop – Magnetic field integrated along closed loop equals current enclosed.

Ampere’s Law for long straight wire •

Right hand rule II • Right hand rule for current carrying wire

Example 20 -7 •

Example 20 -8 •

Example 20 -9

Magnetism in materials • Spinning charge particle creates magnetic field • If all spinning particles align, you have a magnet

Force between parallel wires - 1 •

Force between parallel wires - 2 a) currents same direction b) currents opposite direction action-reaction pair

Magnetism and Induction Flowchart law change field Current force direct examples Force Law 1 B → qv → F = qv x B RHR 1 charge deflection picture tube Force Law 2 B → il → F = il x B RHR 1 2 wires, motor, loudspeaker RHR 2 electromagnet solenoid Lentz generator transformer Ampere’s Law Faraday Induction B = μoi/2πr d/dt → ← i Φ = B*A → ε = dΦ/dt i = ε/R Wire 1 creates magnetic field Wire 2 feels force of that field

Example 20 -10 •

Example 20 -11 •

Problem 41 •

Problem 43 •

Problem 45 •

Rotating current loop •

DC motor • Current reverses every half turn • DC motor

DC Motor animation • DC motor animation • http: //educypedia. karadimov. info/library/Mcc. Complet. swf

Loudspeaker •