Physics 3 — Electricity & Magnetism

Magnetic force — only on the moving

continues from lesson 2 — values defined earlier in the course stay live here

ELI5: a magnetic field ignores a parked charge entirely. Let it move, and the field shoves it sideways — perpendicular to both the velocity and the field: F = q·v·B. A constant sideways push means circles, which is how mass spectrometers and old TV tubes steer beams.

q_{p} = 1.6 \cdot 10^{-19}

one proton (C)

v_{p} = 2000000

speed (m/s)

B_{1} = 0.5

field (T) — a strong lab magnet

F_{m} = q_{p} \cdot v_{p} \cdot B_{1}

1.6 \times 10^{-13}

sideways force (N)

r_{circ} = \frac{1.67 \cdot 10^{-27} \cdot v_{p}}{q_{p} \cdot B_{1}}

0.0418

radius of the proton's circle (m): r = mv/qB

Real-world hook: this sideways force runs electric motors, bends particles in the LHC, and protects us all — Earth's field deflects the solar wind into the auroras.