Physics 3 — Electricity & Magnetism

The field — force per unit charge

continues from lesson 1 — values defined earlier in the course stay live here

ELI5: instead of asking "what force on this charge?", a field maps what any charge would feel at each point: E = k·q/r² (newtons per coulomb). The field is really there, waiting, whether or not anything is present to feel it.

E_{1} = \frac{k_{e} \cdot q_{1}}{r_{q}^{2}}

1.7976 \times 10^{6}

field of q₁ at 10 cm (N/C)

8.988e9 * 2e-6 / x^2

field strength vs distance (m) — the inverse-square cliff

Real-world hook: electric fields steer ink in inkjet printers, fire neurons in your heart and brain (an ECG/EEG reads them), and concentrate at sharp points — which is how a lightning rod works.