TS ECET cheat sheet

Engineering Subject (Branch-Specific)

• Ohm's law and power: V = IR, P = VI = I²R = V²/R; apply per branch before combining series/parallel networks.

• Thevenin equivalent: open-circuit voltage V_th across terminals, R_th found by deactivating independent sources (voltage sources shorted, current sources opened).

• Transformer EMF equation: E = 4.44 f N Φ_max; turns ratio relates voltages directly and currents inversely for an ideal transformer.

• Three-phase power: P = √3 V_L I_L cosφ for a balanced star or delta load; star gives V_L = √3 V_ph, delta gives I_L = √3 I_ph.

• BJT regions: active requires base–emitter forward biased and base–collector reverse biased; cut-off needs both junctions off.

• Op-amp ideal rules: no current into inputs and V₊ = V₋ under negative feedback; inverting gain = −R_f/R_in, non-inverting gain = 1 + R_f/R_in.

• C programming: array index starts at 0; sizeof(char)=1, sizeof(int) is platform-dependent; a string literal always ends with '\0'.

• Data structures: binary search needs sorted input and runs in O(log n); balanced BST operations are O(log n), while hash lookup averages O(1).

• Thermodynamics for mechanical/chemical branches: first law dQ = dU + dW; for an ideal gas isothermal work W = nRT ln(V₂/V₁).