NEET Physics Formula & Conceptual Shortcut Guide
1. Current Electricity & Magnetism
High-Yield Formulas
- Drift Velocity & Current: $I = n e A v_d$, where $v_d = \frac{e E \tau}{m}$.
- Temperature Dependence: $R_T = R_0(1 + \alpha \Delta T)$. For metals $\alpha > 0$, for semiconductors $\alpha < 0$.
- Biot-Savart Law at Axis of Circular Coil: $B = \frac{\mu_0 N I R^2}{2(R^2 + x^2)^{3/2}}$. At center ($x = 0$): $B_0 = \frac{\mu_0 N I}{2R}$.
- Solenoid Field: $B = \mu_0 n I$ (inside) and $B = \frac{1}{2}\mu_0 n I$ (at edges).
2. Modern Physics & Semiconductors
Bohr Atom & Nuclear Physics
- Bohr Radius: $r_n = 0.529 \frac{n^2}{Z}\text{ \AA}$.
- Energy Levels in Hydrogen: $E_n = -\frac{13.6 Z^2}{n^2}\text{ eV}$.
- Rydberg Formula: $\frac{1}{\lambda} = R Z^2 \left(\frac{1}{n_1^2} - \frac{1}{n_2^2}\right)$. Lyman ($n_1 = 1$, UV), Balmer ($n_1 = 2$, Visible), Paschen ($n_1 = 3$, IR).
- Zener Diode: Heavy doping, narrow depletion layer, operates in reverse breakdown region as a voltage regulator.