22.3 Experimental part
F
igure
22.3
-
Assemble the scheme according to figure 21.1. The working point of the frequencymeter is point A (see fig. 22.3). Initial resistance of the generator is 5 Ohm.
-
Set all the switches on the front panel of frequencymeter to positions shown on fig 22.3.
-
Set a measuring limit 7,5 V on the millivoltmeter by turning the switches.
-
Switch on generator and frequencymeter.
-
Select frequency multiplier x100 and set voltage = 10 V on the generator.
-
Changing the frequency of the generator, find the experimental value of the resonance frequency and voltage at resonance. Write down these values in a table 22.1.
-
Measure a resonance curve, i.e. dependence of voltage on the condenser
from
frequency, in a range from 6 kHz to 17 kHz. Thus fluently
increasing frequency observer the values on the millivoltmeter. When
voltage will change on approximately 1 V (20 marks), write down the
value of frequency and voltage in a table. It is not necessary to
try to get the exact meaning of voltage, as the regulator of
frequency of generator is rough and attaining it is impossible.
Table 22.1
|
Ω,kH |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Uc,mV
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
-
Draw the resonance curve on a plotting paper based on experiment results.
-
Choose 5 values of voltage on the condenser and for each of them ind frequencies
and
on
the resonance curve (see fig.22.2). Write down results in a table
22.2.
Table 22.2
|
Ω1, kHz |
|
|
|
|
|
|
Ω2, kHz |
|
|
|
|
|
|
ΩР, kHz |
|
|
|
|
|
-
Using formula (22.7) calculate five values of resonance frequency
and
put them into the table 22.2. Find the mean value of the resonance
frequency. -
Analyze the results, confronting a calculation (
) and directly measured (
) resonance frequencies. If they appear approximately identical,
then it justifies the correlation (22.7), and consequently
expression (22.5) of resonance curve.