| 5. |
Using
an Oscilloscope to compare the frequencies of two supplies of
Alternating Voltage |
|
The
frequency of the main electricity supply has been measured and
was found to be __________.
|
|
a) Obtain a small spot
in the centre of the screen. |
|
b) Connect a 6V a.c.
supply to the B input of the 'scope and adjust the controls to
obtain a vertical line about 4cm long. Now switch off the
6V supply. |
|
c) Connect a signal generator to input A of the
'scope and set its frequency to 50Hz. Now make adjustments to
obtain a horizontal line the same length as the vertical line in
part b).
|
|
d) Switch
on the 6V supply. |
|
e) By making small
adjustments to the signal generator frequency it is possible to
obtain a nearly stationary image on the screen. |
|
When the image is stationary it is
either a i)
_______________________________________________
or ii)
_______________________________________________
or iii)
_______________________________________________ |
|
Conclusion |
|
When the screen
shows one of these shapes, we know that the frequencies of the
two supplies are _________________________ .
|
|
Change the signal generator
frequency to 100Hz. Again, by making small adjustments try to
obtain a stationary, symmetrical image on the screen. Make a
sketch of what you see in the space below. Repeat for 150Hz etc. |
|
f (sig. gen) = 100Hz |
|
f (sig. gen) = 150Hz |
|
Conclusion |
|
The
frequency of the signal generator is given by
f (sig. gen) = 50Hz ×
_____________________ |
|
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