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• Terms and definitions :  
• Magnetic field : Region around the magnet where magnetic force is observed.
• Magnetic field lines : Iron filings sprinkled near magnet get arranged in specific pattern of lines. Such pattern is called as magnetic field lines.
• Magnetic poles : Two ends of magnet (North and South).
• Magnetic south pole : Earth’s north pole is actually magnetic south pole of earth.
• Magnetic north pole : Earth’s south pole is actually magnetic north pole of earth.
• Basic law of Magnetism : Unlike poles attract each other. North pole repel each other.  
• Properties of magnetic field lines :

1. Direction :
• Outside magnet : Directs from north to south.
• Inside magnet : Directs from south to north .
2. Continuity : Magnetic field lines are continuous, hence, form closed curves.
3. Strength : Closer the magnetic  field lines , stronger is magnetic field and vice-versa.
4. Intersection : Magnetic field lines do not cross each other.

• Magnetic field in current carrying conductor : [Refer the video to understand in detail]

Current carrying conductor causes deflection of magnetic needle. If direction of  current is reversed, deflection of needle also gets reversed.

• Pattern of magnetic field : A current carrying conductor produces magnetic field with concentric circular magnetic field lines.
• Right hand thumb rule : “If current carrying conductor is imagined to hold in right hand such that thumb points in direction of electric current then the direction of curved fingers gives direction of magnetic field.”

• Variation of magnetic field :

1. Magnetic field increases with increase in current
2. At constant current, strength of  magnetic field decreases with increase in distance.   

• Magnetic field in current carrying circular loop :
• A straight conductor bent to circle produces magnetic field.
• Magnetic field lines around circular conductor  arranged in concentric circles. Size of circle increase with increase in distance from conductor. At centre biggest circle appears as straight lines.
• Direction of  magnetic field is given by corkscrew rule or right hand thumb rule.
• Corkscrew rule : Imagine ourselves to drive a corkscrew in the direction of flow of current then the direction of corkscrew is the direction of magnetic field.  
• Strength of magnetic field : Strength of magnetic field increases with current and vice-versa. Magnetic field is strong inside the circular loop than that of outside.
• Magnetic field due to solenoid : [Refer the video to understand in detail]
• Solenoid : A straight conductor bent into number of circular turns.
• One end of solenoid behaves as north pole and other as a south pole.
• Magnetic field produced is sum of individual magnetic fields of each turn in the solenoid. Magnetic field inside a solenoid is uniform .
• Force on magnetic field by current carrying conductor :
• A magnetic force is experienced by a current carrying conductor when placed in external magnetic field.
• Direction of force acting on conductor depends on direction of magnetic field and direction of current.  
• Fleming’s Left Hand Rule : “ If forefinger points in direction of magnetic field and middle finger in the direction of current then thumb will point in the direction of the force acting on the conductor.”

• Electric motor :
• Principle of electric motor : A current carrying conductor when placed in magnetic field experiences magnetic force.  
• Construction : Electric motor is consist of  two poles of magnet. In between, two poles a rectangular  loop of insulated copper wire  is placed. Two ends of loop is connected to two halves of split rings and their ends are connected to brushes. Brushes are connected to power source.
• Working : [Refer the video to understand in detail]
1. Current flows through circuit and current carrying conductor experiences magnetic force.
2. Force allows the conductor to move up and down with simultaneous rotation of split rings.
3. At half rotation split rings get connected to brushes, hence direction of  current is reversed, this leads one branch of conductor to move downward and another to move upward. Hence, loop undergoes continuous rotation.
• Modification in commercial motors :
1. Electromagnet is used so as to produce magnetic field, only when current is passed through it.
2. Use to number of turns to form a coil
3. Use of soft iron on which coil is wound, it increases power of motor.
• Electromagnetic induction : Whenever there is change in magnetic flux linked with a conductor, current get induced in it. This is called electromagnetic induction.
• Moving magnet is used to generate electricity : Motion of bar magnet near the conductors induces current in it.
• Current carrying coil induces current in another coil near it : Motion of coil carrying current near another coil induces emf in it. Or. Changing current in one coil induces current in other coil.
• Fleming’s Right Hand Rule : If the thumb, forefinger and middle finger are mutually perpendicular to each other, then, “ forefinger points in direction of magnetic field, thumb points in direction of movement of conductor and current induced is given by middle finger.”
• Electric generator : [Refer the video to understand in detail]
• Principle : It works on Principle of electromagnetic induction. Mechanical energy is used to rotate conductor inside the magnetic field such that current is induced in it.
• Construction : A rectangular coil is placed between permanent magnet. Two ends of coil are connected to two rings each and are attached to axle through insulation. Rings are attached to two brushes each. Brushes are connected with galvanometer.
• Working :
1. Generation of Alternating Current : Mechanical energy is used to rotate armature inside the magnetic field. Hence, current is induced in coil. At half rotation, arm of loop rotate in reverse direction. Thus, direction current through loop reverses. In full rotation direction of current changes after equal interval of time, such current is alternating current. Device used to generate alternating current is called AC generator.
2. Generation of Direct Current : Direct current is produced using split rings. One brush connected to branch always goes up while other connected to branch always goes down. Hence, current is produced in single direction i.e. direct current. Device used to produce direct current is called DC generator.
• Difference between Direct current and Alternating current :

• Domestic electric circuits :
• Household potential difference is 220 V.
• In home circuits there are 3 wires :
1. Live / Line wire : Wire with red insulation. Has high potential of 220 V.
2. Neutral wire : Wire with black insulation. Potential is 0 V.  Gives  return path to current.
3. Ground wire : Wire with green – yellow insulation. Prevents user from electric shock.
• Connection of appliances : Appliances are connected in parallel connection. If one appliance is damaged other won’t get affected.
• Overloading of domestic circuits :  If live wire comes in contact with neutral wire current in circuit abruptly increases leading to short-circuit.
• Condition for short circuit : Bad or damaged insulation, fault in Appliance.
• Precaution from short circuit : Connection of fuse in circuit. Fuse contains wire of metal with lower melting point. In condition of  high current wire in fuse melts, thereby breaking the circuit. Hence, prevent from severe accidents.
• Brief structure of home circuits :

• Live wire and neutral wire runs in house.
• Live wire  connected in series with fuse. It is also connected with electric meter.
• Electric meter tracks electricity usage.
• Distribution box supplies current to individual appliances.
• Ground wire is connected to high power appliances, to get protection from current leaked in metal body.