• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11

Practice A2 Investigation: Measuring the torsion of wire

Extracts from this document...


Kyle Sawhney 12D

Practice A2 Investigation: Measuring the torsion of wire


I decided to investigate how the torsion of wire varies with its length and thickness as it is an interesting, challenging topic which has clearly defined variables. Whilst it is fairly obvious that the torsion of wire would increase as the specimen was made shorter and thicker, the purpose of this investigation was to accurately examine the relationship between the torsion constant of wire, and the variables of length and thickness, using the values of correlation to accurately analyse the effect of these factors and endeavour to explain these conclusions with sound physics knowledge.



The torsion of wire can be measured in a variety of methods, all of which have their merits and drawbacks. The method I chose to employ for this particular investigation was the Torsion Pendulum technique, as all of the necessary materials were available to me in my school laboratory. One of the alternatives to this method was measuring the vertical displacement of a mass hanging from a spring- this method was inappropriate for my investigation as it is far more complex to measure the variables of thickness and length for a spring than for a single uniform piece of wire. Furthermore, I did not have access to a wide array of springs of differing length and thickness with equal mass.

The method for a Torsion Pendulum is as follows:

  • Use a ruler and micrometer to measure the length and thickness, respectively, of a piece of wire
  • Attach the wire to a retort stand, secure at the point of attachment but hanging freely elsewhere
  • Attach a torsion bar to the bottom of the wire using a screw
  • Use a marker as a point from which the period of oscillation can be measured
  • Pull the torsion bar to any sensible angle, (far enough so the data is accurate but not so far that reaction time becomes a major uncertainty) and release it, allowing it to oscillate freely
  • Time the period of the oscillations over an accurate, logistically feasible length of time
  • Repeat this process at least three times for each measurement
  • Repeat the measurement for wires of same length, different thickness or same thickness, different length

A diagram of this experiment is provided below.


The equipment required for this experiment is as follows:

  • Retort stand
  • Selection of wires of different length & thickness
  • Torsion Bar
  • Stopwatch
  • Ruler
  • Micrometer
  • Scales (for measuring mass of torsion bar)
...read more.


Thickness (m)

Period (s)


























These results clearly show a negative correlation between Period and Thickness, a relationship which supports my earlier prediction that the torsion in the wire would increase with thickness. A decrease in Period conveys an increase in torsion as it means the wire is oscillating faster, and thus has greater torsional stiffness. This assertion is corroborated by the measurement of the torsion constant for this data, given below.

Thickness (m)

Torsion Constant











Here, one can clearly see there is a positive correlation between thickness and torsion constant. However, this data doesn’t fully convey the relationship until it is presented graphically, accompanied by an analysis of what the graph demonstrates. Below, I have implemented the data into a scatter graph.

The graph clearly demonstrates that there is an exponential relationship between thickness of wire and torsion constant, a conclusion which makes sense in terms of physics, as an infinitely thick material would be infinitely difficult to twist, just as an infinitely thin material would be infinitely easy to twist. I have also included the equation of the line, and the r² value of the correlation,

y = 0.0003e4309.5x

R² = 0.9863.

The equation of the line demonstrates that it is an exponential relationship, whilst the R² value conveys that there is a very strong positive correlation between thickness and torsion constant.

...read more.


The general conclusions one can glean from this investigation are supported by both the data collected throughout the investigation and the underlying physics of this particular topic; the exponential relationship between torsion constant and thickness of wire was postulated in my original prediction, albeit merely a suggestion of a positive correlation rather than an exponential one, the same is also true for the inverse relationship between torsion constant and length. As discussed earlier, the physics behind these conclusions is fairly rudimentary on the surface (the ruler twisting experimentation etc.), but is in fact much more complicated when one investigates further. Were I to repeat this experiment I would take measurements at the extremes of both thickness & length in order to investigate how large the range of the torsion constant can be. I was unfortunately unable to undertake this experimentation during this investigation as it would require specialist equipment to measure the oscillations of both massive and minute lengths & thicknesses of wire. In addition, it would have been useful to have specialist equipment such as a purpose built Torsion Pendulum rather than having to rely on crude solutions such as the pen lid stopping the vertical oscillations.

In conclusion, I believe this investigation has begun to prove that there is an exponential relationship between torsion and thickness of wire, and an inverse relationship between torsion and length of wire. Whilst it is true these claims cannot be given as wholly true as there is a relative scarcity of data- however, given the time and equipment at my disposal I believe it was a successful investigation undertaken with experimental finesse resulting in conclusions free from any impacting uncertainty.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Modern Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Modern Physics essays

  1. Peer reviewed

    The Compound Pendulum

    5 star(s)

    was suspended freely on a pin after ensuring that the centre of gravity was at 0.5m along the metre rule. This was achieved by applying mass, in the form of blu-tack, to one end of the rule when it was suspended at 0.5m until it reached equilibrium and balanced -

  2. Viscosity Experiment. The aim of my investigation will be to analyse the relationship ...

    the tube was rather large to have light gates around it, however we will not have access to such expensive equipment in the first place. I selected two points on the measuring cylinder, 20 and 80; I thought that this was reasonable because, the ball bearing had approximately 15 cm to reach terminal velocity.

  1. Experiment to calculate spring constant of 2 springs

    Data was then stopped being recorded by pressing the "stop" button in datastudio. This was repeated for the other spring * Using this data, a graph of extension against force could be created, in order to calculate the spring constant for each spring.

  2. Objective To find the acceleration due to gravity by means of a simple ...

    The significant figure of measuring time is 0.01s. It is smaller than the error caused by human reaction. It is a kind of random error. Considering the final result of the experiment, this error will lead to more time measured.

  1. Quality of Measurement - Physics AS

    17 17 x 0.02 = 0.34s 70cm 15 15 x 0.02 = 0.30s 60cm 13 13 x 0.02 = 0.26s 50cm 11 11 x 0.02 = 0.22s 40cm 8 8 x 0.02 = 0.16s 30cm 6 6 x 0.02 = 0.12s 20cm 5 5 x 0.02 = 0.10s 10cm 3 3 x 0.02 = 0.06s Height (cm)

  2. charging a capacitor at a constant rate(C08)

    across capacitor. 3. We should ensure that the capacitor has been fully discharged before being charged up by referring to the 0V reading of CRO. 4. We should use a smaller constant charging current by adjusting the resistor to greater resistance, the capacitor will discharge much slowly, and hence, the charging process can

  1. Building a hovercraft with household objects.

    The pipe should fit snugly into the hole; use silicon caulking to fill in any space between the pipe and the edge of the hole in the wood. After this use duct tape to completely seal the space around the pipe.

  2. Lab Report - In this lab report, it will describe the weight of the ...

    grams attached to a 55 � 0.05 cm, string releasing the bob at 70� � 0.5 having an average time of 1.21 � 0.01 seconds (Table 1). Table 1: The measurements of the pendulum's period with the varied weights of the bobs attached.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work