ELECTROMAGNETIC INDUCTION full.pptx igcse

electromagnetism

1. ELECTROMAGNETIC INDUCTION Generators & Transformers

2. What happens when the wire is been moved in each of the six direction? Straight wire and U-shaped magnet

3. Bar magnet and Coil What happens when the magnet, moves in? is at rest? is removed? How if the coil is moved instead of the magnet?????

4. Electromagnetic Induction Michael Faraday in 1831 (helped by Francesco Zantedeschi) Franz Ernst and Joseph Henry (did not publish their discoveries)

5. About Electromagnetic Induction…. is a process in which a conductor ‘cuts’ through stationary magnetic field lines (or conductor placed in a changing magnetic field) causes the production of a voltage across the conductor. Produces INDUCED E.M.F. and INDUCED CURRENT Constructions of generators and transformers for producing electrical energy in power stations

6. How to increase the induced p.d. or voltage???

7. Faraday’s Law The size of induced p.d. is directly proportional to the rate at which the conductor cuts the magnetic field lines.

8. Direction of the induced current… Lenz’s Law : The direction of the induced current is such as to oppose the change causing it

9. Fleming’s Right Hand (dynamo) Rule

10. Simple a.c. generator rectangular coil Two permanent magnets Two slip rings Two carbon brushes

11. D.C. Generator rectangular coil Two permanent magnets commutator Two carbon brushes

12. Practical Generator Power Stations Rotor & stator rotor: rotating electromagnet Stator : stationary set of conductors wound in coils on an iron core larger p.ds and current induced in stator led away through stationary cables

13. Cars fitted with alternators greater output than dynamo Bicycle Dynamo Rotor: ____________________ Voltage induced in the _______________

14. Mutual Induction when the current in a coil is switched on or off or changed, a voltage is ___________________________ in a neighbouring coil Induced p.d. is increased by:

15. TRANSFORMERS transforms an alternating ______________ from one value to another of greater or smaller value primary coil and _____________ coil wound around on a complete soft iron core

16. Energy loss in a transformer for ideal case: if the p.d. is stepped up, the current is stepped ________ in proportion Electrical energy given to the primary appears in secondary (energy is __________________ ) power in primary = power in secondary Ideal case : if p.d. is doubled, the current ____________ In practice : more than halved due to small energy __________ _

17. Energy losses…. Resistance of windings have resistance and heat produced oil cooled to prevent overheating Eddy currents (current induced in a piece of metal when cuts magnetic field) cause heating laminated core made of sheets insulated from each other Leakage of field lines field lines by primary cuts the secondary (not 100%) (air gap in core or badly designed)