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你看了兩个鐘头的电視广播。在兩个鐘头里,極细的电子射束时強时弱地奔向电视接收机的發光屏。到底有多少个电子为我們扫描景象呢?讓我們来算算看。我們算出,电視管的陽極电流強度平均等于100微安。我們知道在1安培的电流強度下,每秒鐘通过的电荷是1庫侖。不难算出,每秒通过电視管的电荷就是0.0001庫侖。在兩个鐘头里,总共通过的电荷是0.0001×60×60×2=0.72庫侖。我們也知道每个电子所帶电荷为1.6×10~(-19)庫侖。那么,在兩个鐘头內,就有0.72/1.6×10~(-19)=4.5×10~(18)个电子落在發光屏
You watched the two-hour television broadcast. In two hours, the very fine electron beam travels strongly towards the illuminated screen of the television receiver. How many electrons are there for us to scan the scene? Let’s calculate it. We calculate that the TV tube’s anode current intensity is equal to 100 microamps on average. We know that at a current of 1 ampere, the charge per second is 1 coulomb. It is not difficult to figure out that the charge per second through the TV tube is 0.0001 coulombs. In two hours, the total charge passed was 0.0001×60×60×2=0.72 coulombs. We also know that each electron has a charge of 1.6×10-19 coulombs. Then, within two hours, there are 0.72/1.6×10~(-19)=4.5×10~18 electrons falling on the luminescent screen.