Cathode-ray-tube oscilloscopes have parallel metal plates inside them to deflect the electron beam. These plates are called the deflecting plates. Typically, they are squares 3.0 cm on a side and separated by 5.0 mm, with vacuum in between. What is the capacitance of these deflecting plates and hence of the oscilloscope? (Note:This capacitance can sometimes have an effect on the circuit you are trying to study and must be taken into consideration in your calculations.)

A Cathode Ray Oscilloscope (CRO) is an instrument generally used in a laboratory to display, measure and analyse various waveforms of electrical circuits. A cathode ray oscilloscope is a very fast X-Y plotter that can display an input signal versus time or another signal.

given the area A=

Required (0.030 of the deflecting plates and the separated distance between them is d We are asked to find the capacitance C of these deflecting plates_

The capacitance depends on the geometry of the capacitor; it is directly proportional to the area A of each plate and inversely proportional to their separation distance d and it is given by equation 242 in the form

Now We can plug our values for d, eo and A into equation (1) to get the capacitance in Farad where is the electric constant and equals(See Appendix F)

Therefore thecapacitance of deflecting plates andoscilloscopeis