Final answer:
A constant magnetic field can be used to change the velocity of a charged particle.
Step-by-step explanation:
A constant magnetic field can be used to change 3) its velocity.
When a charged particle moves through a magnetic field, it experiences a force called the magnetic force. This force can change the particle's direction of motion, causing it to move in a curved path. As a result, the particle's velocity is affected by the magnetic field.