AP Physics 2 · Exam guide
AP Physics 2 FRQ Guide: Free-Response Habits for Circuits, Gases, Optics and Modern Physics
The AP Physics 2 exam has 40 multiple-choice questions and 4 free-response questions, and the free-response half is 50 percent of your score. The questions mix calculation, graphs, diagrams and short written justifications across thermodynamics, electricity, magnetism, optics and modern physics. Thermodynamics, electric force and field, and circuits are the three largest units. This guide gives you a method that works across all of them.
Four moves that earn points
| Move | What it looks like |
|---|---|
| Write the relationship | Start from the principle or equation, such as Ohm's law or the first law of thermodynamics, before putting in numbers. |
| Show the substitution | Write the numbers with units, so a small arithmetic slip does not hide correct physics. |
| Justify qualitatively | When asked to explain, point to the law and say how it applies, in words and with the direction of any change. |
| Use the diagram | Label a circuit, a ray diagram or a PV diagram, and refer to it in your sentence. |
A worked circuit (made-up numbers)
A 12 V battery is connected in series with a 4 \(\Omega\) resistor and a 6 \(\Omega\) resistor. Find the power dissipated in the 6 \(\Omega\) resistor.
- Series resistance: \(R = 4 + 6 = 10\ \Omega\).
- Current: \(I = V/R = 12/10 = 1.2\) A.
- Power in the 6 \(\Omega\) resistor: \(P = I^2R = (1.2)^2(6) = 8.64\) W.
A follow-up asks what happens to the current if the 4 \(\Omega\) resistor is replaced by a 14 \(\Omega\) one. Compare two answers.
It states a direction but gives no reason.
It names the law, shows the new numbers and gives the result.
Where Physics 2 asks for words
- Qualitative questions about entropy and the second law, where you say what happens to the spread of energy.
- Magnetic force and induced current, where you give directions and name the rule you used.
- Light, such as why a ray bends entering glass, where you refer to speed and the change of direction toward the normal.
- Photons and energy levels, where you tie the energy of a photon to a transition.
Common mistakes
- Putting numbers into an equation with no equation written first.
- Mixing up series and parallel when combining resistors or capacitors.
- Writing a direction (up, left, clockwise) without saying what rule gave it.
- Forgetting that the first law uses work done on or by the gas, and getting the sign backward.
- Leaving units off a final answer.
Frequently asked questions
How many free-response questions are on AP Physics 2?
Four, and the section is half of your exam score.
Which topics are the biggest?
Thermodynamics, electric force and field, and circuits are each about 15 to 18 percent of the exam, together about half of it.
Do I need to memorize formulas?
An equation sheet is provided. You still need to know which relationship applies and what each symbol means.
How do I write a good justification?
Name the law, say how it applies to this situation, and state the result with its direction or size.
Where can I find the official scoring rules?
Exam formats change a little from year to year, so check the current course and exam description on the College Board site before test day.
Keep practicing
Every lesson in the AP Physics 2 course ends with practice items and an Exam focus box, and every unit has a ten-question practice set with worked answers. These free lessons also build the skills the free-response section tests:
- Free lesson 9.3: gas law graphs and experiments
- Free lesson 9.6: PV diagrams, work and thermodynamic processes
See the AP Physics 2 course Free lessons and lesson list
Other free-response guides:
AP is a registered trademark of the College Board, which is not affiliated with and does not endorse this site. This guide is our own explanation of the question types and scoring. For the official scoring guidelines, see the College Board.