1. Electromagnetism Sri. S.P.JANWADKAR Associate Professor & Head
Department of Physics
Karnataka Arts, Science & Commerce College, Bidar
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

2. A moving charge creates a magnetic field
ELECTROMAGNETISM
A moving charge creates a magnetic field
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

3. Right HAND thumb RULE Current flow direction of thumb –
Magnetic filed – fingers
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

4. What is an electromagnet?
When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar 4

5. HOW ELECTRIC & MAGNETIC FIELDS INTERACT
Faraday discovered that the magnetic lines of force and the wire must have a motion relative to each other to induce an electrical current
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

6. ELECTROMAGNET INDUCTION
Moving a wire through a magnetic field will induce a current (Faraday)
Wire or field can move
Moving a magnet through a coil of wire will induce an electrical current
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

7. “Faraday’s Laws : or how to increase the strength of the induced current
Increase the Strength of field or size of magnet
Increase the SPEED of motion
Change the ANGLE (more perpendicular)
Increase the Number of Turns of coil
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

8. ELECTROMAGNETic INDUCTION
MOVING A BAR MAGNET THROUGH A COIL OF WIRE WILL INDUCE A CURRENT TO FLOW THROUGH THAT WIRE
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

9. What are electric motors?
An electric motor is a device which changes electrical energy into mechanical energy.
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar 9

10. How does an electric motor work?
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar 10

11. The principle of the electric motor
To keep the disk spinning, the external magnet must be reversed as soon as magnet (B) passes by.
Once the magnet has been reversed, magnet (B) will now be repelled and magnet (C) will be attracted.
As a result of the push-pull, the disk continues to rotate counterclockwise.
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

12. Generators
A generator is a device that uses induction to convert mechanical energy into electrical energy.
Because the magnet near the coil alternates from north to south as the disk spins,
the direction of the current reverses every time a magnet passes the coil.
This creates an alternating current.
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

13. Transformers
A transformer is a device used to change the voltage in a circuit. AC currents must be used.
75,000 V in the power lines
120 V in your house
p = primary
s = secondary
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

14. Transformers are extremely useful because they efficiently change voltage and current, while providing the same total power.
The transformer uses electromagnetic induction, similar to a generator.
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar

15. Thank you
Department of Physics, KARNATAKA ARTS, SCIENCE AND COMMERCE College, Bidar