NCERT Class 10 The most Important Basic concepts of chapter 13 Magnetic Effects of Electric Current (part-1)

The most Important points of Magnetic Effects of Electric Current (part-1)

1. Magnet and Magnetism: The Substances which have the property of attracting small pieces of iron, nickel, cobalt etc., are called magnets and this property of attraction is called magnetism.

2. Natural magnet: It is a process of Lodestone, which is a black iron oxide (Fe3O4) called magnetite. The word Lodestone means a leading stone.

3. Magnetic poles: The regions of concentrated magnetic strength inside the magnet just near it's ends are called magnetic poles. The pole of a freely suspend magnet which points towards north is called north pole and that points towards south, is called South pole.

4. Law of magnetic poles: It states that like poles repel while unlike poles of magnets attract each other.

5. Basic properties of magnets:

 (i) Magnets attract small pieces of iron, nickel, cobalt,etc.

(ii) When freely suspended, they come to rest in north-south direction.

(iii) Like magnetic poles repel each other and unlike Magnetic poles attract each other.

(iv) The Magnetic poles always exist in pairs.

6. Artificial magnets : Pieces of iron and other Magnetic materials which can be made to acquire the properties of natural magnets are called artificial magnets.

7. Magnetic field: It is the region around a magnet within which it's influence can be experienced.

8. Magnetic line of force: It may be defined as the path in a Magnetic field in which a unit north pole tends to move when allowed to do so. It may also be defined as a curve, the tangent to which at any point gives the direction of the Magnetic field at that point.

9. Compass needle: It is a small Magnetic needle pivoted at the centre of a small circular brass case provided with a glas top. It is used to find the direction of Magnetic field.

10. Magnetic effect of current: A current carrying conductor is always associated with a Magnetic field around it. This is called the ‘magnetic effect of current’. It was first discovered by Haris Christian Oersted in 1820.

11. Magnetic field around a straight current carrying conductor: The Magnetic field consists of concentric circular lines of force around the conductor. The direction of the field is determined by using the following rules:

(i) Right hand thumb rule: If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the Magnetic field.

(ii) Maxwell's corkscrew rules: If a right handed screw be rotated along the wire so that it advances in the direction of current, then the direction in which the screw rotates gives the direction of the Magnetic field.

12. Factors on which the Magnetic field produced by a straight current carrying conductor depends: It is directly proportional to the current passing through the wire and inversely proportional to the distance from the wire.

13. Magnetic field of a circular current carrying coil: Near the circumference of the wire, the Magnetic lines of force are almost straight and parallel. Hence, near the centre, the Magnetic field is uniform and normal to the plane of the loop.

14. Solenoid: A long cylindrical coil of insulated copper wire of large number of circular turns is called a solenoid. A current carrying solenoid behaves like a bar magnet. Polarity of its any end can be determined by using clock rule by nothing the direction of the flow of current. If the current is anticlockwise, the end is a north pole and if the current is clockwise, the end is a South pole.

15. Electromagnet: It is a solenoid with a soft iron core placed inside it. When current is passed through the solenoid, the soft iron core becomes a temporary Magnet. The strength of an electromagnet can be increased by

(i) increasing the number of turns per unit length of the coil, 

(ii) increasing the strength of current, and

(iii) winding the coil over a soft iron core. 

16. Force on a current carrying conductor placed in a Magnetic field: In 1820, Ampere demonstrated that a current carrying conductor placed in a Magnetic field experiences a force. If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both and is given by Fleming's left hand rule.

17. Fleming's left-hand rule: This rule gives the direction of the force exerted on a current carrying conductor placed in a Magnetic field. According to this rule if we hold the thumb, the forefinger and the central finger of the left hand mutually perpendicular to each other and if the forefinger points in the direction of the Magnetic field, central finger in the direction of the current, then the thumb points in the direction of motion (or the force) on the conductor.

18. Factors on which the force experienced by a current carrying conductor placed in a Magnetic of depends: The force F exerted on a conductor of length L, carrying current I and placed perpendicular to a Magnetic field B is given by

                 F = BIL

No force is exerted on a stationary charged particle in a Magnetic field.

19. SI unit of Magnetic field is Tesla (T) : One Tesla is that Magnetic field in which a charge of one coulomb moving with a velocity of 1m/s perpendicular to the Magnetic field experiences a force of one Newton.

20. Electric motor: It is a device to convert electrical energy into mechanical energy. It is based on the principle that when a current carrying coil is placed in a Magnetic field, it experiences a torque. Our daily appliances such as electric fans, washing machines, mixers and blenders use electric motors.