Chapter 22 - Physics Notes

Electric Generator: A device that converts mechanical energy into electrical energy using electromagnetic induction.
Alternating Current (AC): Electricity characterized by the periodic change of voltage polarity and current direction within a circuit.
Direct Current (DC): Electricity that flows in a single direction without changing polarity.
Inductance (L): The property of a conductor that opposes a change in electric current by producing a magnetic field that induces an opposing potential difference.

Alternating Current Generation

A simple generator uses a rotating magnet and a loop of wire to induce current.
Current alternates direction during each rotation, creating a sine wave pattern.
Effective (rms) potential difference: $V_{rms} = \frac{V \max}{√2}$
Three-phase generators use three pairs of coils for efficient power delivery.

Generated using a split-ring commutator to convert AC to DC.
DC motors operate by converting electrical energy into mechanical work.
Back emf: An induced emf in a motor that opposes the supplied current, reducing overheating risks.

Inductance Formula

L = \frac{n φ}{I}

Transformers

Step-up transformer: Increases voltage; secondary has more turns than the primary coil.
Step-down transformer: Decreases voltage; secondary has fewer turns than the primary coil.

Power Transmission: High-voltage AC is transmitted over long distances for efficiency.
Smart Grids: Advanced electricity distribution systems with improved efficiency and reliability.
Induction Heating: Uses eddy currents to heat metal cookware directly.