## Wednesday, April 07, 2010

### [Science Form 3] Electricity

Electrical energy
• Definition: Energy produced when an electric current flows.

• The source of electrical energy is any device that produces electric charges or electric current.

Electricity
• Definition: The flow of electric charges through a conductor.

• Electrons flow in the direction opposite to the electric current. The electric current is the rate of flow of electric charges passing through a conductor.

• The unit of electric current (I) is ampere.

• The unit of voltage (V) is volt.

• The unit of resistance (R) is ohm.

• Different materials have different resistance to electricity.

• The resistance of a conductor is affected by its length, diameter and temperature.

• A very high resistance allows only a very small amount of current to flow.

Van De Graaff generator

The Van De Graaff generator is a device that can produce electric charges of very high voltage. When the motor is turned on, the lower roller (charger) begin turning the belt.

As the belt is made of rubber and the lower roller is covered in silicon tape, the lower roller will begin to build a negative charge while the belt builds a positive charge.

The negative charge on the lower roller is built up by capturing electrons from the belt as it passes over the roller. This occurs as silicon is more negative than rubber in the triboelectric series.

#### 1 comment:

1. nice article..this is cool alternative solution to save our planet earth

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