DIY Stationary Waves On A String Experiment For The Price Of A Pizza
We have replicated the A Level Physics required practical Stationary Waves On A String experiment, which would typically cost hundreds for the equipment alone, for a fraction of the price of the equipment you would typically use in High School.
It's a fun project for those interested in physics and experimenting with waves and you can reuse the parts in loads of other projects.
By replicating the Stationary Waves On A String experiment using homemade and inexpensive equipment, you can gain a deeper understanding of wave behavior and the properties of standing waves on a string.
Overview
Here we will give an overview of the equipment, experiment, principals, and show you how to make a really simple solenoid.
More Resources
Performing The Experiment
Our other article focuses specifically on performing the Stationary Waves On A String experiment, with step-by-step instructions and analysis of the results.
So even if you don't want to make your own and just want to understand the required practical you can check out our separate article and video on the topic.
We cover:
- Overview of the experimental procedure and the goals of the investigation
- Stationary Waves, Harmonics, Nodes and Antinodes
- Detailed explanation of the steps involved in performing the experiment, including measuring frequency, wavelength, and tension
- Discussion of data analysis techniques and interpretation of results
- Shared Google Spreadsheet with our results, calculations and graph you can reuse
- Recap of key points and a call to action to perform the experiment and analyze the results
Building The Equipment
We have a detailed easy to follow article focused on building the experimental equipment, and links to the github code you can read here
Apperatus
We have a string which is fixed at one end. The other end hangs over a pulley and is attached to a mass to create the tension in the string.
We clamped a big allen key to a desk to provide a fixed point to hold the end of the string. There are many altearnatives such as a heavy lamp, monitor arm, or even some bricks.
For the pulley, we used a lego wheel with the tire removed. The groove was perfect for the string. We build a lego mount and clamped it to the desk.
At School you would use a mass hanger and some masses. We replaced this with a rain jacket stuff sack and some batteries.
You need to be able to change the length of the string, at school you would use a wooden bridge but we used a set square taped to a box.
Now to vibrate the string at School you would use a signal generator, vibration generator, and oscilloscope. We replaced all this with a solenoid operated by a cheap Raspberry Pi Pico RP2040 running some basic micro python code.
You will also need a tape measure or meter rule to measure your length of string, some scales to measure the mass, and of course some string.
We bought some very accurate scales from Amazon for under £4. You could use kitchen scales instead.
Solenoid
We picked up some very cheap solenoids from AliExpress. We also got some from Amazon.com which were 4 times the price but still quite cheap.
The solenoid will create a magnetic field when a current is applied which will attract a metal shaft to be pulled down into it.
When the current is removed a spring will pop the metal shaft back up. The simple circuit and microcontroller will turn the current on and off at specific frequencies to create the vibration.
Make Your Own Solenoid
We advise you buy a solenoid but for fun and to learn we build a simple solenoid from some spare wire and a screw.
We coiled the wire around a pencil and attached it to a 9 volt battery. This produced a magnetic field which lifted up a screw.
We were really impressed at how well this worked, adding a fixed magnet to the screw made it even stronger.
The Experiment
The Stationary Waves On A String experiment investigates the properties of waves on a string, specifically standing waves. Standing waves are formed when two waves traveling in opposite directions interfere with each other, creating points of no movement (nodes) and points of maximum movement (antinodes).
The experiment involves creating a standing wave on a string by vibrating it at a certain frequency and measuring the wavelength, frequency, and tension in the string. By changing the length of the string and repeating the measurements, we can investigate the relationship between these properties and gain a deeper understanding of wave behavior.
To perform the experiment, we first set up the apparatus as described above, with the string attached to a mass to create tension and one end fixed. We then used the solenoid to vibrate the string at various frequencies to find the 1st, 2nd, and 3rd harmonic.
We identified the harmonic from the number of nodes/antinodes present.
We did this for various lengths of string by moving the bridge (our set square on a box).
From our results we could confirm the relationship of frequency of the harmonics. Wave speed using multiple methods, and even the mass of 1m of string.
Summing Up
Replicating the Stationary Waves On A String experiment using homemade and inexpensive equipment is a fun and educational project that can be done at home.
By building the apparatus and performing the experiment, you can gain a deeper understanding of wave behavior and the properties of standing waves on a string.
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