Question

The x and y sensitivities of an analog oscilloscope are set as 2 ms/cm and 1 V/cm respectivley. The trigger is set at 0 V with negative slope. An input of $2cos(100\pi t+{30}^o)V$ is fed to the y input of the oscilloscope. The wave form seen on the oscilloscope will be

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

$X-sensitivity=2msec/cm=S_X$
$Y-sensitivity=1V/cm=S_Y$

for input peak to peak voltage,
$V_{P-P}=4V$

So, length on Y-axis form peak to peak,
$l_1=\frac{V_{PP}}{S_Y}=4cm$

$\Rightarrow T=\frac{2\pi }{\omega }=\frac{2\pi }{100\pi }=\frac{1}{50}=20msec$
$\Rightarrow T/2=10msec$

Now half cycle on X-axis corresponds to legnth,
$I_2=\frac{T/2}{S_x}=\frac{20msec}{2msec/cm}=5cm$
This is shown in figure (a) only.