Key idea
Magnetic field
Force magnétique : F = |q|vB sinθ
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Magnetic field
The key idea
Magnetic fields act on moving charges and magnetic dipoles. Their effects depend on direction as well as magnitude.
Why it matters
The magnetic force on a moving point charge is perpendicular to both velocity and field, so it can bend a trajectory without directly changing the particle’s speed.
A picture to remember
Key idea
Magnetic field
Guided example
Magnetic field
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Put it into practice
Magnetic field
Choose a concrete case linked to Magnetic field. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.