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