Comprehensive notes for Chapter 15 Electromagnetism. Covers Magnetic Effects of Current, Key Rules (Right Hand Grip, Fleming's Left Hand), D.C. Motor, electromagnetic Induction, A.C. Generator, and Transformer.
Electromagnetism: Study of magnetic effects of current. Current passing through a conductor produces a magnetic field around it.
Straight Wire: Field lines are concentric circles. Direction found by Right Hand Grip Rule (Thumb = Current, Curled Fingers = Magnetic Field).
Solenoid: A coil of many turns. Field resembles a bar magnet. Field strength increases with current and number of turns.
A current-carrying conductor placed perpendicular to a magnetic field experiences a force.
F = ILB \sin \alpha
Where $I$=Current, $L$=Length, $B$=Magnetic Field Strength, $\alpha$=Angle.
Direction: Determined by Fleming's Left Hand Rule (Thumb = Force, Forefinger = Field, Middle Finger = Current).
Device: Converts electrical energy into mechanical energy.
Principle: A current-carrying coil placed in a magnetic field experiences a torque (Couple) which rotates the coil.
Construction: Coil (Armature), Magnet, Split Ring Commutator (Reverses current direction every half cycle), Brushes.
Torque: $\tau = NIAB \cos \alpha$. (Depends on Current, Turns, Area, Field).
Definition: Production of induced current in a circuit by changing the magnetic flux through it.
Faraday's Law: Induced EMF is directly proportional to rate of change of magnetic flux.
Lenz's Law: Direction of induced current is such that it opposes the cause that produces it (Conservation of Energy).
Device: Converts mechanical energy into electrical energy.
Principle: Coil rotates in magnetic field, changing flux induces alternating EMF.
Components: Coil, Magnet, Slip Rings (Maintain connection while rotating), Carbon Brushes.
Mutual Induction: Production of induced current in secondary coil due to change of current in primary.
Transformer: Device to increase/decrease AC voltage. Works on Mutual Induction.
\frac{V_s}{V_p} = \frac{N_s}{N_p}
Ideal Transformer: Input Power = Output Power ($V_p I_p = V_s I_s$).