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There are two types of guitars, acoustic guitars and electric guitars - Leaving Cert Physics - Question 9 - 2020
Question 9
There are two types of guitars, acoustic guitars and electric guitars. In acoustic guitars resonance occurs between the vibrating strings and other parts of the gui... show full transcript
Worked Solution & Example Answer:There are two types of guitars, acoustic guitars and electric guitars - Leaving Cert Physics - Question 9 - 2020
Step 1
Step 2
Describe a laboratory experiment to demonstrate resonance.
Answer
To demonstrate resonance, one can set up a simple experiment using a tuning fork and a resonating chamber.
Apparatus: A tuning fork, a resonating chamber, and a sound level meter.
Method: Strike the tuning fork gently and bring it close to the opening of the resonating chamber. Measure the sound intensity using the sound level meter as you adjust the distance between the fork and the chamber to find the point where the sound is amplified due to resonance.
Observation: At specific distances, the sound intensity will increase significantly, indicating resonance.
Step 3
Draw a labelled diagram to show a guitar string vibrating at its fundamental frequency.
Answer
A labelled diagram should include a representation of the guitar string with nodes and antinodes clearly marked. The points where the string is fixed (nodes) should be at either end, and the center should be an antinode where vibration amplitude is maximal.
Step 4
Calculate the tension in the string.
Answer
The linear density of the string is given by:
u = \frac{m}{L} = \frac{0.88 \times 10^{-3} \text{ kg}}{2 ext{ m}} = 4.4 \times 10^{-4} \text{ kg/m}$$ Using the fundamental frequency relationship: $$f = \frac{1}{2L} \sqrt{\frac{T}{\nu}}$$ Substituting the known values: $$330 = \frac{1}{2 \times 2} \sqrt{\frac{T}{4.4 \times 10^{-4}}}$$ This leads to: $$T = 4.4 \times 10^{-4} \times (2 \times 330)^2$$ Thus, we can calculate the tension in the string.Step 5
Calculate the speed of sound in the string.
Answer
The speed of sound in the string can be calculated using the formula: Where:
- is the tension calculated previously,
- is the linear density of the string. After calculating , substituting the values will yield the speed of sound in the string.
Step 6
Step 7
Explain how an emf is induced in the coil.
Answer
An electromotive force (emf) is induced in the coil when the magnetic field around the coil changes. As the guitar string vibrates, it alters the magnetic field's strength passing through the coil. According to Faraday's law of electromagnetic induction, a changing magnetic flux will induce an emf in the coil.
Step 8
Sketch a graph to show how the output current varies with time.
Answer
The graph should be a sine wave representing alternating current, oscillating above and below the time axis. The frequency of the wave should correspond to the vibration frequency of the guitar string. The axes should be labeled time on the x-axis and current on the y-axis. The current should vary smoothly, showing the periodic nature of the output.