UPDATED: 16 Ideas for IB Physics IA Investigations

I’ve had over... hits on my first blog post for this subject.

I’ve updated it with advanced information, as it is obviously a post that offers lots of value to readers.

I get emails every day from students who have found Guzled online and are looking for help with finding a topic for their IB Physics Internal Assessment.

Here’s an example:

Most IB Physics teachers will have been met with similar requests from their students. I have sympathy – I remember harassing my own physics teacher for an idea for my sixth form Physics Investigation!

I Can Help With IB Physics IA Ideas

This blog post goes into more detail on each of these ideas.

You can simply download the ideas quickly below.

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IB Ethos and Personal Engagement

In theory, I support the ethos of the IB and students should be encouraged to come up with their own investigation, based on their own interests; however, I feel strongly that a list of possible investigation titles would be useful when introducing the IB internal assessment investigation to the students.

Not every student will be able to come up with an original idea. As long as they find an investigation that sparks their imagination and can produce workable results – they shouldn’t have to agonise one their topic for weeks.

The new IB syllabus uses five criteria to assess the final report of the students individual investigation. These criteria are below, with the associated weighting:

  1. Personal Engagement (8%)
  2. Exploration (25%)
  3. Analysis (25%)
  4. Evaluation (25%)
  5. Communication (17%)

Whilst Personal Engagement may hold the smallest weighting, it it still important to adhere to the IB ethos and encourage your students to investigate something they are interested in.

Here’s How I’ll Help – 16 Ideas

In this post, I’m going to provide 16 actionable ideas for IB Physics IA, including advice on which variables might be good to investigate.

I will also highlight what your student’s personal engagement might be and how they will link in to the investigation.

Idea 1
How does the tension and diameter of a string affect the fundamental frequency?

This investigation is a pretty standard physics experiment. It will generate workable data, with nice graphs that are easy to analyse. It can be set up at the back of a lab, with no expensive equipment.

The student will have to determine which independent variable to investigate. They could choose from:

  • Tension in the string
  • Diameter of the string
  • Mass per unit metre of the string
  • Temperature of the string

Perhaps the length of the report will mean that they have to investigate more than one variable.

Student’s Personal Engagement:     string instruments (guitar, violin, etc)

Here is a link to my worksheet for investigating the tension in a string, which can be used in classroom teaching.

Idea 2
How does sugar concentration affect the refractive index of water?

When you take a tank containing concentrated sugar solution and gently pour on a layer of water – there will be a difference in densities of the solutions. A laser beam shone into this tank will bend, depending on the concentration of sugar solution (and hence the difference in liquid densities). The difference in densities of air is this effect that causes mirages in the desert!

A great experiment would be to vary the concentration on the sugar solution and to measure the refractive index.

The student would have to fully investigate the best method for determining the refractive index of a liquid.

Student Interests:     refractometers, fizzy drinks, wine, etc

Idea 3
How does the voltage across the accelerating electric field affect the spacing of the diffraction pattern of the electron diffraction?
(using a Teltron Tube)

Independent Variable: Accelerating Voltage

Dependent Variable: Distance between the central point of the diffraction pattern and the 1st order maximum

This investigation is really interesting.

With careful data collection and a bit of maths, the results are linear and very pleasing. It is also possible to use the results and determine the spacing between the planes in the atomic lattice of graphite, using the de Broglie Relationship.

The error analysis in this investigation is detailed, but satisfying!

Student’s Personal Engagement: Particle Accelerators, Electron Microscopes, Wave-Particle Duality

Here is a link to my worksheet and sample data for investigating electric diffraction that can be used in classroom teaching.

Idea 4
How does temperature affect the viscosity of fluids?

Finding the viscosity of a fluid is a fairly standard sixth form experiment. You would simply use castor oil and ball-bearings of variable sizes.

The method for finding the viscosity of a fluid can be found here

The following apparatus is needed.


(It is also possible to use light sensors and a computer to measure time intervals or indeed a webcam linked to the computer to record the fall of the ball bearings.)

In theory, the viscosity of the fluid changes with temperature. A great experiment would be to plot the variation in temperature with the viscosity.

Student’s Personal Engagement:     Sweet making / ketchup etc

Here is a link to my worksheet for determining the viscosity of castor oil.

Idea 5
Investigate factors that affect the flight of an elastic band

You could interpret this investigation in many ways. Firstly, you should decide what the dependent variable means to you in this.

Personally, I would look at the the range of the elastic band. This is easily measured and there are loads of independent variables that will be measurable too.

Dependent Variable: Range

With this is mind, there are lots of independent variables that can be investigated:

Possible Independent Variables:

  • Temperature of elastic band;
  • Angle of launch;
  • Length of elastic band;
  • Width of elastic band;
  • Thickness of elastic band;
  • Strain of the elastic band upon launch;

The list is endless.

This also means that the control variables should be carefully addressed in this investigation – making it an excellent project for differentiation of abilities.

Rubber Band

Student’s Personal Engagement:     Catapults

Idea 6
Investigate the Young Modulus of materials

There are different methods of measuring the Young modulus of a material.

An interesting project could be to investigate which method of finding Young Modulus is most accurate, compared to a textbook value under the same conditions.

Possible methods include:

Student’s Personal Engagement:     Fishing, Suspension bridges

Click here to link to my worksheet for determining the Young Modulus of a wire using the tabletop method (it’s from a different exam board but the method is the same!)

Idea 7
Investigate the factors affecting the internal resistances of cells.

Finding the internal resistant of a cell is a common and standard sixth form physics practical. However, it could be extended to look at how the internal resistance of a cell varies under certain conditions. Some of these might include:

  • How does the internal resistance of a cell vary with temperature?
  • How does the internal resistance of a cell vary with length of usage?
  • How does the internal resistance of a cell vary with the type of cell?

Addressing these questions could take a standard sixth form investigation into an interesting and informative project.

Student’s Personal Engagement:     Battery life in high tech appliances

Click here to link to my worksheet for determining the internal resistance of a cell

Idea 8
Investigate the factors that affect fluid damping of an object in SHM

If energy is removed from a system undergoing simple harmonic motion (by friction), its amplitude will decrease. This usually follows an exponential decay pattern.

Friction due to viscosity will eventually dissipate the initial energy input to an oscillator and it will return to its position of stable equilibrium. This is called damping.


There are lots of experiments that can be done with fluid damping and the maths is super-pleasing!

You could measure the exponential decay of amplitude for an oscillating system. This will vary depending on the conditions of damping.

The independent variables chosen could be:

  • Area of damping card
  • Viscosity of surrounding fluid
Student’s Personal Engagement:     Suspension systems

Idea 9
Investigate magnetic braking

Magnetic braking relies on eddy currents. It is caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source (e.g. a magnet) and conductor. Eddy currents are set up in the conductor and these can act as a brake on the motion (Lenz’s Law).

This effect can be seen when a magnet is dropped down a copper pipe. Watch this really short video below:

Possible magnetic braking systems to investigate:

  • Connector.

    Magnetic Braking: Sliding Down an Incline

    If you let a magnet slide down an incline on a sheet of tinfoil then the braking current can be observed when compared to a control.

  • Connector.

    Magnetic Braking: Supermagnet Pendulum

    If a pendulum is allowed to oscillate between two pieces of aluminium (or other metal) the eddy currents should slow it down.

  • Connector.

    Magnetic Braking: Toy Car

    Fix a neodymium iron boron magnet to the underside of a toy car with a rubber band and let it run down a wooden incline. Experiment with various materials, angles, masses, etc.

Student’s Personal Engagement:     Magnetic suspension systems

Click here for my worksheet for a Lenz’s Law practical.

Idea 10
Investigate factors that affect the surface tension of water

Surface tension is the reason that spiders can walk on water and we cannot!


Surface tension is defined as the amount of energy required to increase the surface area of a liquid by a unit amount.

A good investigation would be to look at how surface tension changes with concentration of soap or with temperature.

An appropriate method of determining surface tension would have to be researched first.

Student’s Personal Engagement:     Pond skaters

Idea 11
Investigate factors affecting the lift produced by a model helicopter

The rotor blade of a helicopter forces air downward. Newton’s third law requires that the air in turn exert an equal force upward on the rotor. For a helicopter to hover, the force exerted by the rotor blade on the air must be equal to the weight of the helicopter.


It is possible to measure the lift of a model helicopter using an electronic balance. Recording the difference between the mass of the helicopter when the rotor blades are not moving and then when rotating, will allow the lift force to be calculated.

Possible factors affecting the lift could be:

  • Rotor shape;
  • Rotor angle;
  • Rotor size;
  • Number of rotor blades;
  • frequency of rotation;
  • Temperature of surrounding air.
Student’s Personal Engagement:     Flight

Idea 12
How does sugar concentration affect the optical activity of a solution?

Sugar is optically active because the molecules themselves have a twist in them. When linearly polarized light passes through aa sugar solution, its direction of polarization is rotated. The angle of rotation depends on the concentration of the solution and the wavelength of the light. You could make up a solution of sugar (sucrose) and hydrolyse it using dilute acid. As the reaction proceeds, the degree of polarisation changes. The student would have to work out a suitable way of measuring the rotation of polarisation.


Possible factors could be to investigate how the angle by which the polarization plane of light is rotated in a sugar solution depends on:

  • the wavelength of the light;
  • the concentration of the solution;
  • the layer thickness (path travelled by the light in the solution);
  • the temperature of the sugar solution.
Student’s Personal Engagement:     Refractometers / fizzy drinks / wine/ telescopes

Idea 13
Investigate the factors affecting the efficiency of a motor

The efficiency of a motor is pretty easy to determine.

The following factors could be investigated to see how they affect the efficiency:

  • No. of coils;
  • Radius of magnets;
  • Radius of coils;
  • Strength of magnets;
  • Input current.

The list is endless and this could make a very interesting investigation.

Student’s Personal Engagement:     Motor Sport, ecological machines

Idea 14
Factors affecting the efficiency of a transformer

Exam calculations often assume transformers are 100% efficient. They are not.

However, it is one of the most efficient machines because there are no moving mechanical parts in a transformer, therefore it is highly efficient. The efficiency is increased further by:

  • Using thick copper wires of low resistance, to keep the resistance in wires (and resulting heat loss) to a minimum;
  • Using laminated layers in the iron core to reduce the formation of eddy currents;
  • Using a closed soft iron core to improve the transmission of induced magnetic flux.


A great investigation would be to investigate the numerical efficiency of a transformer and how it changes by adjusting the factors above.

Student’s Personal Engagement:     Global energy transportation, electrical engineering, globalisation

Click here for my worksheet on how to calculate the efficiency of a transformer

Idea 15
Determine the width of a human hair using diffraction

When waves approach a barrier, they diffract around it. The same happens whens laser light approaches a strand of hair.


The diffraction pattern can be observed on a screen, placed some distance from the hair in a darkened room.


Simple geometry allows us to determine the width of the hair strand, b(m), through use of the following expression:



  • λ is the wavelength of the laser light (which is written on the laser.)
  • b is the width of the strand of hair.
  • θ is the angle subtended between the screen, central maxima and the first minimum. It can be found using trigonometry.

There could be an extended and interesting investigation in this.

Idea 16
How the voltage across two oppositely charged metal plates affects the frequency of metal-covered a ping pong ball oscillating between them

Two oppositely-charged parallel plates will produce an electric field between them.


The electric field strength, E, between the two plates can be calculated using:


Where V is the potential difference across the two plates (in Volts) and d is the distance between the two plates (in meters).

If a ping-pong ball is given a metal covering (e.g. aluminium foil) and is suspended between two parallel plates with a high potential difference across them, the ball will bounce back and forth between the plates; touching each plate in turn and collecting charge from the plate. This causes it to repel from the plate and accelerate to the other plate. The greater the potential difference across the plates, the greater the charge collected and thus the faster the frequency of oscillation.

It is expected that as the potential difference increases, the frequency of oscillation of the ping pong ball will increase.

The Details of the Investigation

Each pupil in Higher or Standard Level Physics should complete one piece of internally assessed coursework. This will be in the form of an investigation and should take no more than 10 hours. Note that this is not 10 hours of lab work, but 10 hours to complete:

  • Time spent introducing the internal assessment
  • Class time to carry out experiments and ask questions;
  • Time spent on consultation and feedback;
  • Time spent reviewing progress and authenticity;

10 hours does not include write-up time.

It should be around 2000 words long, so it’s certainly not equal to the undertaking required for an Extended Essay. Only this one piece of practical work will be assessed. It accounts for 20% of the final mark and is internally assessed by the teacher and externally moderated by the IB. The other required practicals are not assessed directly, but will be examined.

That’s a completely different blog post…..

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Sally is the Guzled founder and, more importantly, a part-time physics teacher at Mary Erskine School in Edinburgh. She led a large and vibrant department for 7 years, after training to teach in London. She is a Trustee for Dynamic Earth, an IoP Teacher Network Co-ordinator, a Practical Advisor for AQA and guest lecturer for Stirling University.

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