Thursday, February 25, 2010

don't confuse about resistance!!!!!

Why nichrome wire not , used in bulb???
Because the nichrome wire not heat up larger as tungsten wire. Tungsten wire suitable to build as filament in bulb , as the current increases the temperature rises and the resistance goes up. Its not obeys ohm's law. The resistance of a piece of nichrome increases by only about 1% for a 100 degree celcius. tungsten filament heats up to 3000 degree celcius. At this temperature, its resistance is about double then when cold. eventhough, Nichrome suitable used as heating elements in kettles,hairdryers.

energy from battery

Students !!! Do you know

When elctrons are pushed out of a battery, they carry energy with them.in the circuit, the elctrons use all their energy passsing through the bulb . The energy chnage into heat. and light.
When the electrons reach the battery again, all their energy has gone.The higher the voltage , the more energy is given to each electron.