4.3. Motion in Electromagnetic Fields (D3)

In combined fields, charged particles experience forces from both electric and magnetic fields, affecting their motion (e.g., in a velocity selector).

Electric and magnetic forces can balance each other, or create complex particle paths such as helical motion.

These interactions are foundational for devices like mass spectrometers, cathode ray tubes, and particle accelerators.

A moving charge in a magnetic field experiences a force perpendicular to both its velocity and the magnetic field.

In a uniform magnetic field, if velocity is perpendicular, the particle moves in a circular path due to centripetal force provided by the magnetic force.

If the velocity has components both parallel and perpendicular to the field, the path becomes a helix.

Direction of deflection reveals the sign of the charge (positive or negative).

Radius of circular motion in a magnetic field depends on mass, speed, charge, and field strength.

Magnitude of acceleration or curvature allows calculation of the particle’s mass-to-charge ratio, important in identifying unknown particles.