Electrical Resonance - Research and rationale.
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Introduction
Azeem Mir
Electrical Resonance
Research and rationale
I have chosen to investigate the resonance in circuits after studying digging up the past and technology in space modules. Also my knowledge in electronics has been useful as it allowed me to understand the behavior of the apparatus, such as an oscilloscope, and the principles used in the investigation. I have used the physics principles for capacitance and inductance where the combined impedances cancel each other out or reinforce each other to produce a minimum or maximum impedance. Impedance is the alternating-current equivalent of resistance.
For my research I am going to look on the internet for any relevant information about resonance and the type of circuits it appears in. Also I will look back at the A-level physics textbook which contains the “Digging up the past” and “Technology in space” modules to refresh what I already learnt about resistance.
For each circuit, resonance occurs at a given frequency called the resonant frequency, which depends on the amounts of inductance and capacitance in the circuit. If an alternating voltage of the resonant frequency is applied to a circuit in which the capacitance
Middle
All the signal voltages in the experiment will be small and harmless. The mains voltage in the mains powered equipment is dangerous but is screened in normal use. Also no food or drink will be brought into or consumed in the lab and the work area will be clear of all but essential apparatus and equipment.
Method
- Firstly I will be collecting and setting up the apparatus shown in the diagram above.
- I will then ensure the inductor is set on 10mH, ensure the capacitor has a value of 7000pF and set the decade resistance box to 20Ω.
- then I will connect one input of the oscilloscope between A earth to measure Va and the other input between B and earth to measure Vb.
- I will then adjust the oscilloscope to display stable traces of Vb and Va simultaneously.
- Once this has all been completed I will look for the resonant frequency by slowly adjusting the frequency of the signal generator until the maximum of Vb meets Va sharply (in-phase).
- I will then repeat the experiment for different combinations of inductors and capacitors and record my findings.
Accuracy and sensitivity
For my results I will aim to record values up to 3 decimal points and keep this consistent throughout my results.
Conclusion
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0.020
50.00
40Ω
0.018
55.56
50Ω
0.015
66.67
60Ω
0.013
76.92
70Ω
0.012
83.33
80Ω
0.011
90.91
90Ω
0.010
100.00
100Ω
0.009
111.11
Log frequency | Log L*C | |
1 | 1.25 | 4.93 |
2 | 1.54 | 4.31 |
3 | 1.36 | 4.69 |
4 | 1.04 | 5.34 |
5 | 1.71 | 3.96 |
6 | 1.53 | 4.34 |
7 | 1.42 | 4.58 |
8 | 1.2 | 4.99 |
Conclusion
From my experiment I have successfully shown that resonance occurs in a RLC circuit. I have also shown the formula regarding resonance: 
is true by calculating the slope on my graph of
log LC against log frequency which was -0.48 verifying the square root in the formula.
Limitations
The limitations to my results are that there wasn’t a very large frequency range on the signal generator which would allowed me to utilize an even lager combination of inductors and capacitors which would have produced me more detailed graphs. Also I didn’t have the time or equipment to observe resonance in other types of circuits like the types found in radios and televisions which would have given me the chance to see whether the formula applied to these circuits.
Modifications
I could have modified the experiment by utilizing a signal generator with a larger frequency range allowing me to use combinations of inductors and capacitors where the resonant frequency is either extremely high or low.
Further experiments
I could further the experiment by observing the way resonance works in radios and televisions and how the circuits achieve it. This would provide me with a deeper understanding and larger knowledge of electronic resonance and its applications.
Bibliography
[1] “Resonance (electronics)” - Microsoft Encarta encyclopedia.
[2] The physics of resonance - www.intuitor.com/resonance
This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.
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