## 07 July 2011

### cbse class 10th Magnetic Effects of Electric Current notes and key points

Class -  10th Chapter 13- Magnetic Effects of Electric Current

KEY POINTS

1. Magnetic field and lines of force: The region in which a magnetic force can be detected is called magnetic field. Field lines are used to represent a magnetic field. A field line is the path along which a free north pole tends to move.

2. The direction of magnetic field at a point is given by the direction which a north pole placed at that point would take.

3. Electro-magnetism: Whenever current is passed through a conductor, it produces a magnetic field around it. This phenomenon was discovered by H.C.Oersted.

4. The magnetic field lines around a current carrying wire is in the form of concentric circles whose direction is given by the right hand thumb rule. The strength of field due to a current carrying conductor depends on the strength of the current and the distance of the conductor to the point considering.

5. Magnetic field due to a circular coil depends on the strength of current, radius of the loop and the no. of turns of the coil.

6. Magnetic field due to a solenoid carrying current is similar to that of a bar magnet.

7. Electro magnet consists of a core of soft iron wrapped around with a coil of insulated copper wire. Hard steel and alloys like nipermag, alnico etc are used for making permanent magnets, while soft iron is used for temporary magnets.

8. A current-carrying conductor placed in a magnetic field will experience a force. The magnitude of this force depends on the length of the conductor, current flowing through it and the strength of magnetic field. The direction of force acting on a current-carrying conductor is given Fleming’s left hand rule. An electric motor is a device based on the above principle in which electric energy is converted into mechanical energy.

9. The phenomenon in which an induced current is produced in a coil due to the relative motion between a magnet and the coil is called electro-magnetic induction which was discovered by Michael Faraday. The direction of induced current is given by Fleming’s right hand rule. An electric generator is a device based on electro-magnetic induction in which mechanical energy gets converted into electrical energy. In domestic circuits, all appliances are connected in parallel. Fuse is the most important safety device, used for protecting the circuits due to short circuit or overloading