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'A' Level Questions - The Oscilloscope

Q3. A cathode ray oscilloscope is used to study the waveform of a sinusoidal alternating voltage of frequency 100 Hz and peak voltage 2.0 V. If the time base is set to 2.0 ms div–1 and the voltage sensitivity is 0.5 V div–1, draw, in the grid below, the trace you would expect to see on the screen.

Remember that an oscilloscope is a voltmeter that plots you a voltage time graph on the screen. In an exam mark on the values from the settings so that you can interpret the information easily.

You need to do some calculations in order to draw the trace.

Peak voltage is the amplitude - that is 2.0V.

There are 0.5V per division so the amplitude will be 4 divisions - and peak to peak will be 8 divisions.

Frequency is 100 Hz.

period T = 1/f = 1/100 = 0.01s = 10 ms - 5 divisions

two full traces will therefore fill the screen

Marks are awarded for:

    • the shape - sinusoidal wave (line gradient must be changing and distance between crests and troughs symmetric)
    • correct amplitude
    • correct time period
    • two cycles drawn

(Total 4 marks)