AP Physics 2 units and review
AP Physics 2 moves beyond mechanics into heat, electricity, magnetism, light and modern physics. Here is what each unit covers.
On this page
The units
- Thermodynamics: temperature, heat, the ideal gas law and the laws of thermodynamics.
- Electric force, field and potential: charges, Coulomb's law, fields, potential and capacitors.
- Electric circuits: current, resistance, series and parallel circuits and Kirchhoff's rules.
- Magnetism and electromagnetism: magnetic fields, forces on charges and currents, and induction.
- Geometric optics: reflection, refraction, lenses and mirrors.
- Waves, sound and physical optics: interference, diffraction and the wave model of light.
- Modern physics: photons, the photoelectric effect, energy levels and nuclear physics.
Check unit names, order and weightings in the current course and exam description on AP Central.
How to review
- Use our AP Physics 2 equation sheet guide to link each equation to its topic.
- For circuits, practise redrawing and simplifying before calculating.
- For fields, draw field lines and equipotentials to build intuition.
- For optics, practise ray diagrams until they are quick and accurate.
- Practise free-response questions that ask you to explain, not just calculate.
Where students struggle
- Sign conventions in thermodynamics and optics.
- The difference between electric potential and potential energy.
- Direction rules for magnetic forces and induced current.
One example per unit
- Thermodynamics: a gas absorbs 400 J of heat while 150 J of work is done on it. ΔU = 400 + 150 = 550 J.
- Electric force and field: a 2 µC charge in a 3000 N/C field feels F = qE = 0.006 N.
- Circuits: a 6 Ω and a 3 Ω resistor in parallel combine to 2 Ω.
- Magnetism: a proton moving at 2 × 105 m/s at 90° to a 0.1 T field feels F = qvB ≈ 3.2 × 10−15 N.
- Geometric optics: an object 20 cm from a converging lens with f = 10 cm forms an image 20 cm on the other side.
- Waves and physical optics: for a double slit with d = 0.1 mm and λ = 600 nm, the first bright fringe is at sinθ = 0.006.
- Modern physics: a 500 nm photon has energy E = hc/λ ≈ 2.5 eV.
How the topics connect
- Electric fields lead to potential, which drives current in circuits.
- Moving charges create magnetic fields, and changing magnetic fields induce emf.
- Light behaves as a wave in interference and as a particle in the photoelectric effect.
Practice questions
Try each one before opening the answer.
Q1. Two 4 Ω resistors in series are connected to 16 V. Find the current and the power dissipated in one resistor.
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Q2. Light goes from glass (n = 1.5) into air. Above what angle of incidence does total internal reflection occur?
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Q3. Why does brighter light not give photoelectrons more kinetic energy?
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Frequently asked questions
Should I take AP Physics 2 after AP Physics 1?
Physics 2 builds on Physics 1 skills. Students heading toward life sciences or medicine often take it; engineers often choose Physics C instead.
Which unit is hardest?
Many students find magnetism and induction hardest because of the direction rules. Practise right-hand rules with lots of quick examples.
The key ideas in more depth
Thermodynamics
Temperature measures the average kinetic energy of particles. Heat is energy transferred because of a temperature difference. The first law, ΔU = Q + W, is conservation of energy for a gas. PV diagrams are central: the area under a PV curve gives the work done, and a closed loop represents a cycle such as an engine.
Electric potential and circuits
Electric potential is energy per unit charge. A battery raises charges to a higher potential, and they lose that energy as they pass through resistors. Kirchhoff's loop rule says the potential changes around any closed loop add to zero; the junction rule says current into a junction equals current out. Together they solve any circuit in the course.
Magnetism and induction
Magnetic fields push on moving charges and currents, at right angles to both the field and the motion. A changing magnetic flux through a loop induces an emf. Generators, transformers and induction hobs all depend on this.
Light: waves and particles
Geometric optics treats light as rays that reflect and refract. Physical optics treats it as a wave that interferes and diffracts. Modern physics shows it also behaves as particles (photons). Each model works in its own situations, and the course asks you to choose the right one.
Exam tips
- Label PV diagrams with the direction of each process.
- Redraw circuits neatly before solving them.
- Practise ray diagrams for converging and diverging lenses until they are quick.
- Use energy-level diagrams for photon emission and absorption questions.
More practice
Try each one before opening the answer.
Q1. A gas goes round a cycle on a PV diagram clockwise. Is net work done on or by the gas?
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Q2. An electron drops from the −3.4 eV level to the −13.6 eV level in hydrogen. Find the photon energy.
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One more worked example
Example: a mirror image
An object stands 30 cm in front of a concave mirror with focal length 10 cm. Find the image distance and magnification.
- 1/si = 1/10 − 1/30 = 2/30, so si = 15 cm in front of the mirror (real image).
- Magnification M = −si/so = −0.5: the image is inverted and half the size.
Extra practice
Try each one before opening the answer.
Q1. A capacitor of 4 µF is connected to 6 V. Find the charge stored and the energy stored.
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Q2. Two point charges repel with force F. If the distance between them doubles, what is the new force?
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More questions students ask
Is AP Physics 2 harder than AP Physics 1?
It covers more varied topics, but students who did well in Physics 1 usually find the reasoning skills carry over.
Key takeaways
- Physics 2 covers thermodynamics, electricity, magnetism, optics and modern physics.
- Kirchhoff's rules solve any circuit in the course.
- Changing magnetic flux induces an emf.
- Light behaves as both a wave and a particle.
- Practise ray diagrams and PV diagrams until they are quick.