Light ~

Ok.In fact, it's because some of the electrical energy changed into heat energy.In fact,over 90% of electrical energy changed in heat and only about 2-4% of electrical energy changed into light energy.
As you notice the problem of energy waste is serious, you can choose to use a compact fluorescent lamp instead of ordinary light bulb. Also, you can use LED(light emitting dioude, dioudes which can emite light by the semi-conductor,its waste is very low) or T5 light .
Hope this can help you..
bye

**hope you can choose this as the best ans. ,thx**

2009-01-15 16:10:47 補充：
oh..there are three kinds of methods to spread heat.
對流(液體+氣體作介質)
傳導(固體作介質))
radiation(不需任何介質)

2009-01-15 16:11:02 補充：
而光管的就是radiation

2009-01-16 12:54:48 補充：
好的好的,用中文沒問題.
這樣好了.:
在流向燈泡的電能中,有部分會由電能轉成了熱能,成了能源的浪費,約90%以上的電能也是轉化成熱能,然而,卻只有2-4%的電能轉成光能,可見其浪費很大.
那麼,為什麼電能會轉換成熱能呢?這是因為電流的熱效應.當有電流通過任何有電阻的物質時,部分電能就會轉換成熱能.保險絲就是應用了這個效應而生效的(保險絲能保護電路,不會受過大電流玻壞,就是當電流過高時,保險絲會因高溫而熔斷(溫度高過其熔點),能斷開電路)
而我們可選用慳電膽/T5光管來解決及降低所做成的浪費,而LED也是一個很好的選擇.

以上的全是我個人的答案喔,別抄襲..

When electricity pass through the bulb, the electric energy causes the bulb to emit light, but there are some energy that is not used to emit light, they are the heat (and sometime there could be sound). The energy is not fully used to emit light, that is why beside of the light, you feel the heat through radiation.

2009-01-15 22:39:57 補充：
當電流經過燈泡時，電力的能量會令燈泡發出光，但那些能量當中有些不是用來發光的，那些是熱能(甚至有時候會變為聲音)。那些能量並不是完全用作發光的，因此當你站近那燈光時，你會感到那熱能以輻射方式傳遞。

answer is The Bulb Emitting Infrared For Us