Wednesday, July 12, 2017

A cathode-ray oscilloscope (c.r.o.) is connected to an alternating voltage. The following trace is produced on the screen. ...





Question 1
A cathode-ray oscilloscope (c.r.o.) is connected to an alternating voltage. The following trace is produced on the screen.


The oscilloscope time-base setting is 0.5 ms cm-1 and the Y-plate sensitivity is 2 V cm-1.
Which statement about the alternating voltage is correct?
A The amplitude is 3.5 cm.
B The frequency is 0.5 kHz.
C The period is 1 ms.
D The wavelength is 4 cm.





Reference: Past Exam Paper – June 2014 Paper 12 Q3





Solution 1:
Answer: B.

Amplitude is the maximum voltage. It can be obtained by considering the vertical position of the trace from the central line on the screen.
Y-plate sensitivity = 2V cm-1
Amplitude = 3.5 cm = 3.5 × 2 = 7 V
[A is incorrect]

Frequency = 1 / period = 1 / T
A value of time (not ‘wavelength’) can be obtained horizontally. [D is incorrect]
Time-base setting = 0.5 ms cm-1
Period T = 4 cm = 4 × 0.5 = 2 ms       [C is incorrect]
Frequency = 1/T = 1 / (2×10-3) = 0.5 kHz

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