What does the trace on a cathode ray oscilloscope screen show?

It shows the potential difference applied to the input plotted vertically against time running horizontally, so the shape of a varying signal can be seen directly.

What is the function of the y-gain control on an oscilloscope?

It sets the vertical sensitivity in volts per division, so the number of divisions the trace is deflected multiplied by that setting gives the potential difference.

What is the function of the time-base control on an oscilloscope?

It sets the horizontal sweep rate in seconds per division, so the number of divisions occupied by one cycle multiplied by that setting gives the period of the signal.

Describe how the peak voltage of an alternating signal is found from an oscilloscope trace.

Count the number of divisions from the central horizontal line to the top of the trace and multiply by the y-gain setting in volts per division.

How is the peak voltage obtained if the peak-to-peak height of the trace has been measured?

The peak voltage is half the peak-to-peak value, because the trace extends equally above and below the zero line for a symmetrical alternating signal.

CCEA A-Level Physics 1210

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Practical Skills and Data Analysis

Using the cathode ray oscilloscope to measure voltage and frequency

3 things to know
Units AS 3 and A2 3

Overview

Function of the y-gain control on an oscilloscope and function of the time-base control on an oscilloscope.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe how the frequency of a signal is found from an oscilloscope trace.

Numbers

The time-base is set to 0.20 ms per division and one cycle occupies 2.5 divisions. Calculate the frequency of the signal.

Key term

State the relationship between the period and the frequency of a signal, with the units of each.

Questions from this subtopic

Each one with the model answer underneath.

1
What does the trace on a cathode ray oscilloscope screen show?
Model answer
It shows the potential difference applied to the input plotted vertically against time running horizontally, so the shape of a varying signal can be seen directly.
2
What is the function of the y-gain control on an oscilloscope?
Model answer
It sets the vertical sensitivity in volts per division, so the number of divisions the trace is deflected multiplied by that setting gives the potential difference.
3
What is the function of the time-base control on an oscilloscope?
Model answer
It sets the horizontal sweep rate in seconds per division, so the number of divisions occupied by one cycle multiplied by that setting gives the period of the signal.
4
Describe how the peak voltage of an alternating signal is found from an oscilloscope trace.
Model answer
Count the number of divisions from the central horizontal line to the top of the trace and multiply by the y-gain setting in volts per division.
5
How is the peak voltage obtained if the peak-to-peak height of the trace has been measured?
Model answer
The peak voltage is half the peak-to-peak value, because the trace extends equally above and below the zero line for a symmetrical alternating signal.
6
Describe how the frequency of a signal is found from an oscilloscope trace.
Model answer
Measure the number of horizontal divisions occupied by one complete cycle, multiply by the time-base setting to obtain the period T in seconds, and calculate the frequency from f = 1/T in hertz.

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