5 Structured Questions – Cathode Ray Oscilloscope

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Diagram \(4.1\) shows a bright spot, P, formed on the screen of a cathode-ray oscilloscope, C.R.O. when it is switched on.

  1. What is the meaning of cathode ray? [1 mark]
    High speed election beam.
  2. Explain how the bright spot is formed on the screen of the C.R.O. [2marks]
    When the electrons hit the fluorescent screen, the screen glows and forms a light spot. The kinetic energy of the electrons changes to light energy.
  3. Diagram \(4.2\) shows the bright spot is displaced to \(Q\) when a direct current, d.c. supply, is connected to the Y-input of the C.R.O.

The Y-gain of the C.R.O is set at \(2 V /\) division. Calculate the input voltage of the d.c. supply. [2 marks]

Output voltage
\[
\begin{aligned}
&=2 V +2 V \\
&=4 V
\end{aligned}
\]

  1. Diagram \(4.3\) shows an alternating current, a.c. supply, is connected to the C.R.O. The Y-gain of the C.R.O. remains at \(2 V /\) division.

Draw the output signal on the screen in Diagram \(4.3\) when the peak voltage of the a.c. supply is \(6 V\) and the time base is switched off. [2 marks]