Monday, September 24, 2007

Resistance

Electrical resistance is a compute of the degree to which an object opposes an electric current through it. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance calculated in siemens. Electrical resistance shares some conceptual parallels with the mechanical notion of friction.
The resistance of an object determines the amount of current through the object for a known voltage across the object I=V/R, where R is the resistance of the object, measured in ohms, equivalent to J•s/C2, V is the voltage across the object, measured in volts, I is the current through the object, measured in amperes. In metals, the Fermi level lies in the conduction band giving rise to free transfer electrons. However, in semiconductors the position of the fermi level is within the band gap, closely half way between the conduction band minimum and valence band maximum for intrinsic semiconductors.

Wednesday, September 5, 2007

Beach volleyball

Beach volleyball is an Olympic group sport played on sand. Two teams, positioned on either side of a net which divides rectangular court, hit volleyball, usually using the hands or arms. It is evolved from indoor volleyball, and the two sports remain very similar: a team scores points by foundation the ball on the opponents' court, or when the opposing team commits a fault teams can contact the ball no more than three times before the ball crosses the net; and consecutive contacts must be made by unlike players. The most important differences between beach and indoor volleyball are the playing surface, and the team size. There are many minor differences as well, including each half of the court actions 8 by 8 meters.
If a jamming player touches the ball, but it continues onto his side of the net, the block counts as the first contact. Open-hand dinks, where a player uses his or her finger tips to redirect the ball into the opponent's court, are banned. It is legal to cross under the net as long as doing so does not hamper with the opponents' attempt to play the ball. Players are not necessary to rotate positions; they must alternate check, but there are no rotation errors.