Ans: Principle: A current-carrying conductor placed in a magnetic field experiences a mechanical force (motor effect). The force direction is given by Fleming's Left Hand Rule. Main components: (1) Armature coil — rectangular coil of insulated copper wire, mounted between poles of a magnet. (2) Permanent magnet — provides the magnetic field. (3) Split ring commutator — reverses the direction of current in the coil every half rotation, ensuring continuous rotation in the same direction. (4) Carbon brushes — maintain electrical contact between commutator and external circuit. (5) Battery/power source — provides current. Electric motors convert electrical energy into mechanical energy. Used in fans, mixers, washing machines, electric vehicles.

Ans: Faraday's First Law: Whenever the magnetic flux linked with a circuit changes, an EMF (electromotive force) is induced in the circuit as long as the change lasts. Faraday's Second Law: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux. EMF = -ΔΦ/Δt. Lenz's Law: The direction of the induced current is always such that it opposes the change (increase or decrease) in magnetic flux that caused it — consistent with conservation of energy. Example: moving a magnet toward a coil induces a current that creates a magnetic field opposing the approaching magnet (the coil's face becomes like a N pole repelling the magnet). This is why generators require mechanical work.

Ans: Oersted's Experiment (1820): Place a compass needle on a table. Hold a straight wire parallel to the compass needle just above it. When no current flows, the compass needle points north (Earth's field). Connect the wire to a battery — current flows through the wire. Observation: The compass needle deflects immediately, pointing perpendicular to the wire. Reverse the current direction — the needle deflects in the opposite direction. Conclusion: A current-carrying conductor produces a magnetic field around it. The direction of the magnetic field (circular field lines) around the wire is given by the Right-Hand Thumb Rule: thumb in direction of current, curled fingers show field direction.

Ans: DC (Direct Current): flows in one direction only; supplied by batteries and solar cells; used in electronic devices, charging. AC (Alternating Current): periodically reverses direction; frequency in India is 50 Hz (changes direction 100 times/second); voltage 220V. AC is used in households because: (1) It can be easily stepped up/down using transformers — making long-distance transmission efficient (high voltage = low current = less heat loss in wires). (2) AC generators are simpler and more efficient than DC generators. (3) Most household appliances are designed for AC. (4) AC is cheaper to generate and distribute. DC is used where AC is not suitable (electronics, batteries, variable speed motors).

Ans: Electric motor: A device that converts electrical energy into mechanical (rotational) energy. Working: A rectangular coil ABCD is placed between the poles of a permanent magnet. When current flows through the coil, the magnetic field exerts a force on each arm (Fleming's Left-Hand Rule): F = BIl. The forces on AB and CD are in opposite directions, creating a torque that rotates the coil. A split-ring commutator reverses the current direction every half rotation, keeping the rotation in the same direction. Commercial importance: Used in electric fans, water pumps, refrigerators, washing machines, mixers, electric vehicles, industrial machinery. Fleming's Left-Hand Rule: Stretch thumb, index, and middle fingers mutually perpendicular — index points in direction of magnetic field, middle in direction of current, thumb gives direction of force on conductor.

Ans: Electromagnetic induction is the phenomenon of generating an electric current (or EMF) in a conductor by changing the magnetic flux linked with it. Discovered by Michael Faraday (1831). Key observation: When a magnet is moved into or out of a coil, or when the current in a nearby coil changes, an induced current flows in the coil. Faraday's Law: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux. Lenz's Law: The induced current is in a direction such that it opposes the change causing it (conservation of energy). Application: Electric generators, transformers, induction cooktops, electric guitars.