A.2.12—Field forces
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- HL
Separate Gravitational, Electric and Magnetic Forces
Three field interactions
Gravitational, electric and magnetic forces are field forces: bodies can interact without contact. Identify the source of the field, the object acted on and the force direction.
Keep the mechanisms distinct
Gravity acts on mass, electric force acts on charge, and magnetic force acts on moving charges or currents in a magnetic field. Their equations and direction rules are not interchangeable.
Use the force relevant to the system
A free-body diagram may contain more than one field force. Add them as vectors and apply Newton’s second law to the selected body.
Common trap
Do not call every non-contact force “electromagnetic”; gravitational attraction is a separate interaction.
A.2.12 Exam Analysis
Assessment in practice
1–2 marksHow it is assessed
The evidence asks learners to identify fundamental forces and to list the forces acting on quarks, testing recognition of electric, weak, strong and gravitational interactions.
Command terms
List / Identify
What earns marks
Identify the relevant field interaction and state what the force acts on. Distinguish gravity, electric and magnetic forces by their source and by whether mass, charge or motion/current is required.
Watch for
Treating the three field forces as interchangeable or omitting the interaction condition that distinguishes magnetic force from electric force.
Representative question
Question 1
[Maximum number: 1]
What are three fundamental forces listed in decreasing order of strength?
A
Strong nuclear, gravity, electromagnetic
B
Electromagnetic, strong nuclear, gravity
C
Strong nuclear, electromagnetic, gravity
D
Gravity, weak nuclear, electromagnetic
C