IB Physics IA Guide (2026)

If you ask most IB students what worries them about Physics, many will say the exams. But from a teacher’s perspective, the Internal Assessment (IA) is where students often lose — or gain — the most marks.

The reason is simple.

The IA is not about how much you know. It’s about how clearly you apply physics in a real investigation.

Over the years, I’ve seen students with strong concepts score poorly because their IA lacked structure, while others with average understanding scored 20+ simply because they approached it correctly.

This guide is meant to help you do the latter.

Who This Guide Is For

This article is written for IB Physics students in:

• Grade 11 and Grade 12
• Both SL and HL

A quick clarification — the IA is assessed using the same criteria for SL and HL. The only difference is that HL students are usually expected to show slightly deeper analysis.

How the IB Physics IA Is Actually Marked

Your IA is graded out of 24 marks, divided into four parts:

Research Design (6 marks)

This looks at how clearly you define your research question, variables, and method.

Data Analysis (6 marks)

This is where most marks are won or lost. It includes graphs, uncertainties, and calculations.

Conclusion (6 marks)

You must directly answer your research question using your data and relate it to physics theory.

Evaluation (6 marks)

You are expected to identify errors, discuss limitations, and suggest realistic improvements.

From experience, the biggest issue is not the experiment — it’s weak analysis and evaluation.

Choosing a Topic: Where Most Students Go Wrong

Students often think they need a unique or complex idea. That’s rarely true.

A good IA topic is not impressive — it is clear, controlled, and measurable.

Use This Simple Format

Your research question should look like:

“How does X affect Y?”

This keeps your investigation focused and makes analysis much easier.

For example:

• How does the length of a pendulum affect its time period?
• How does voltage affect current in a circuit?

Both are simple, but if done properly, they can score very high.

What Makes a Strong IA Topic

Before finalizing your idea, check the following:

It should be measurable

You need numerical data, not observations.

It should be feasible

You should be able to perform the experiment with available equipment.

It should be controlled

You must clearly define:

• Independent variable
• Dependent variable
• Control variables

It should connect to the syllabus

Stick to core topics like mechanics, electricity, waves, or thermal physics.

Reliable IB Physics IA Topic Ideas

These are common topics — and that’s perfectly fine.

• Pendulum length vs time period
• Spring mass vs oscillation period
• Wire length vs resistance
• Voltage vs current in a circuit
• Surface type vs friction

What matters is not the idea, but how carefully you carry out the investigation.

Designing Your Experiment Properly

A well-planned method makes everything easier later.

Define Your Variables Clearly

For example:

• Independent variable: length of pendulum
• Dependent variable: time period
• Control variables: mass, amplitude, air resistance

If this is unclear, your IA will lose marks right from the start.

Write a Clear Method

Your method should be:

• Step-by-step
• Easy to follow
• Repeatable

If another student cannot repeat your experiment, your method is incomplete.

Repeat Measurements

Take at least three readings for each value and calculate an average.

This improves reliability and strengthens your data analysis.

Data Analysis: The Real Difference Between Average and High Scores

This is where strong IAs stand out.

Include Uncertainties

Every measurement should include uncertainty. Ignoring this is one of the most common reasons students lose marks.

Draw Proper Graphs

A good graph must include:

• Axis labels with units
• A best-fit line
• Error bars

Show Your Calculations

Include:

• Averages
• Gradients
• Final values with uncertainty

Explain What the Data Means

Avoid simply describing graphs.

Instead of saying “the graph is linear,” explain what that implies in terms of physics.

Structure That Works

You don’t need anything complicated. A clear structure is enough:

1. Introduction
2. Variables
3. Method
4. Data Collection
5. Data Analysis
6. Conclusion
7. Evaluation

Keep your writing focused. Avoid adding unnecessary theory.

Common Mistakes to Avoid

Some patterns appear again and again:

• A vague research question
• Missing uncertainties
• Poorly labeled graphs
• Weak evaluation
• Overcomplicated experiments

The strongest IAs are usually simple but carefully executed.

A Practical Timeline

A structured approach helps avoid last-minute stress:

• Week 1–2: Choose topic and plan
• Week 3–5: Perform experiment
• Week 6–7: Analyze data
• Week 8: Write and refine

Final Advice

If there’s one thing worth remembering, it’s this:

A high-scoring IA is not about doing something complicated. It’s about doing something clear, controlled, and well explained.

Focus on:

• A simple experiment
• Careful data collection
• Strong analysis
• Honelligent evaluation

That combination consistently leads to high marks.