How electricity is generated Key points

5.9 How electricity is generated Key points

1. A D.C. generator produces a unidirectional voltage and current.
2. The three major parts of a D.C. generator are stator, rotor and commutator.
3. The direction of the induced e.m.f. in straight conductor is determined by the Right-Hand Rule.
4. The direction of the induced e.m.f. in coil conductor or solenoid is determined by the Right-Hand Grip Rule.
5. Electrical energy may be generated by ways other than magnetism and chemical action.
6. A piece of electric crystal can generate electricity when subjected to a changing pressure across two of its sides (compressed or released).
7. A steady pressure applied to a piece of electric crystal will not generate electricity.
8. The most frequently used piezoelectric crystals are quartz, Rochelle salt and barium titanate.
9. Electricity is produced whenever there is a relative motion between two materials such as a glass rod and silk. This is called static electricity. We can simply say that electricity is produced by friction.
10. Radiant energy is another source of electricity:
a. a photovoltaic cell converts light energy into electricity,
b. all photovoltaic cells are composed of two layers of dissimilar semi-conductor materials.
11. When a light ray strikes the junction between the two layers of a photovoltaic cell, electrons are forced across it.
12. Modern solar cells are made of silicon and germanium semi-conductor material.
13. Geothermal energy is heat energy produced within the Earth.
14. Geothermal power is renewable and environmentally friendly.