The net result is that a 5% reduction in the voltage more than doubles the life of the bulb, but delivers 20% less light.
综上所述，减少电压5%能使灯泡的使用寿命延长至少2倍，但是其亮度会下降20%。
2
Just like with your flashlight that you have at home, you sometimes have to put in several cells in series to get a higher voltage so that you can power a small light bulb.
就像你家里的，手电筒，你有时必须，放几个电池，来达到一个更高的电压，以此点亮一个小灯泡。
3
What is the ratio between the thermal energy and light energy emitted from a small electric bulb depending on the voltage applied to a bulb?