The cathode ray oscilloscope (CRO) is a type of electrical instrument which is used for showing the measurement and analysis of waveforms. It is a very fast X-Y plotter shows the input signal versus another signal or versus time. It is like plotting a graph of an electrical signal. Being able to use an oscilloscope is avaluable skill for any person learning about electrical circuits. 

In this experiment multiple electrical circuit components are used. A power supply that puts out an AC signal which has a sine wave waveform. There are also two decade boxes (a unit containing resistors of many values, with one or more mechanical switches which allow any one of various discrete resistances offered by the box to be dialed in), a capacitor and a wire coil. One decade box is always included in the system but the second decade box, the capacitor and the coil are swopped out and changes in the waveform analysed. The resiatnce of the decae box can also be changed and the wwaveform analysed using the oscilloscope. 

This experiment familarises students with all the tools of the oscilloscope and how changes in waveforms can be seen and measured using the oscilloscope. 

Somevirtual oscilloscope you can try out are:

Interactive Online Virtual Oscilloscope and Signal Generator

Virtual Oscilloscope