Describe magnetic fields and poles qualitatively, and compute the magnetic force on a moving charge or a current-carrying wire.
Every magnet has two poles, north and south, that can never be isolated from each other -- breaking a magnet in half simply creates two smaller magnets, each with its own complete north and south pole, unlike electric charge, which comes in genuinely separable positive and negative units. Like poles repel and opposite poles attract, mirroring electric charge behavior, and a magnetic field maps the direction a compass needle would point at each location around a magnet. Earth itself behaves like a giant, tilted bar magnet, which is why a compass needle reliably aligns with it.
Magnetism and electricity are deeply linked: a moving electric charge creates a magnetic field, and a magnetic field exerts a force on a moving charge -- but never on a stationary one. That force is F = q*v*B*sin(theta), maximized when velocity and field are perpendicular (theta=90) and zero when they are parallel (theta=0). The same idea extended to a whole current-carrying wire gives F = B*I*L*sin(theta), with the force's direction found using the right-hand rule.
Mastery looks like: They compute the magnetic force on a moving charge or a current-carrying wire using F=qvB or F=BIL, and correctly explain why only moving charge experiences a magnetic force.
Common stumbles: Applying the magnetic force formula to a stationary charge; forgetting the sin(theta) factor when velocity or current is not perpendicular to the field.