Question

Which of the following are true, regarding magnetic fields and forces?

a Magnetic field lines exit the south pole of a bar magnet and enter its north pole.
b Magnetic forces can perform work on charged particles.
cThe maximum magnetic force on a charged particle occurs when the particle's velocity is parallel to the magnetic field.
d If a charged particle is moving in circles in a magnetic field, and the radius of its circular path is decreasing, its speed must be increasing.

Answer 1

Magnetic field lines, magnetic forces, parallel velocity, and decreasing radius.

Step-by-step explanation:

Regarding magnetic fields and forces:

1. True: Magnetic field lines exit the south pole of a bar magnet and enter its north pole.
2. True: Magnetic forces can perform work on charged particles.
3. False: The maximum magnetic force on a charged particle occurs when the particle's velocity is perpendicular to the magnetic field, not parallel.
4. True: If a charged particle is moving in circles in a magnetic field and the radius of its circular path is decreasing, its speed must be increasing.

So, options a and b are true, option c is false, and option d is true.