使用示波器做實驗與到的一些問題

Question

1)我把一條cable插入cro既ch.1到(x-input).然後把手掂著佢既頭部(即無插入果邊),點解示波器上會有波形顯示?這些body signal係邊到黎?
2)我把第二條cable同時插入ch.2到,每隻手都各掂著一條cable既頭部,點解個波形既vertical高度細左?
thank you!

修正:
2)我把第二條cable同時插入 - ch.1(x-input)到,每隻手都各掂著一條cable既頭部,點解個波形既vertical高度細左?

Answer 1

There are static charges on your body, your skin, fingers and clothes that would give a small but unsteady voltage, detectable by the CRO.

When you touch the cables with two hands, the CRO tends to measure the potential difference between the two inputs (i.e. the p.d. across the two cables), which is practically very small as there should be no steady voltage across your body. Thus the signal is reduced.