Electrical & Mechatronics — Cheat Sheet
Ohm's law, power, motors, DC basics for the mechanical engineer.
Ohm's-law triangle: cover the unknown — V = I·R, I = V/R, R = V/I.
DC fundamentals
| Ohm's law | V = I·R |
| Resistance | R = ρL/A |
| Series R | R = R₁ + R₂ + … |
| Parallel R | 1/R = 1/R₁ + 1/R₂ + … |
Power
| Electrical power | P = V·I = I²R = V²/R |
| Energy | E = P·t |
| Efficiency | η = P_out / P_in |
Motors
| Mechanical power | P = T·ω = 2πnT/60 |
| DC motor emf | V = I·R + k_e·ω |
| Torque | T = k_t·I |
| Power (hp↔W) | 1 hp = 746 W |
AC & signals
| RMS (sine) | V_rms = V_peak / √2 |
| Reactance (L) | X_L = 2πfL |
| Reactance (C) | X_C = 1/(2πfC) |
| Time constant | τ = RC or L/R |
Formula reference — verify against the governing standard. Not a substitute for engineering judgment.