### FIELD FORMULAS (B in Tesla = [$MT^{-2}$$A^{-1}$])
| Source | Formula |
|---|---|
| Infinite wire | B = μ_{0}I/(2πd) |
| Circular loop (centre) | B = μ_{0}NI/(2R) |
| Circular loop (axis) | B = μ_{0}N$IR^{2}$/[2($R^{2}$+$x^{2}$)^(3/2)] |
| Solenoid (inside) | B = μ_{0}nI, n = N/L |
| Toroid (inside ring) | B = μ_{0}NI/(2πr) |
### FORCE FORMULAS
| Situation | Formula |
|---|---|
| Moving charge | F = qvB sinθ (⊥ to v; no work) |
| Conductor | F = BIl sinθ |
| Between parallel wires | F/l = μ_{0}$I_{1}I_{2}$/(2πd) |
| Torque on loop | τ = NIAB sinθ = MB sinθ |
### CIRCULAR MOTION
- Radius: r = mv/(qB) [depends on v]
- Period: T = 2πm/(qB) [INDEPENDENT of v — NEET trap!]
- Frequency: f = qB/(2πm)
### GALVANOMETER CONVERSIONS
- Ammeter: S = I_gG/(I − I_g) in PARALLEL (low resistance)
- Voltmeter: R = V/I_g − G in SERIES (high resistance)
### MATERIALS
- Dia: χ < 0; μᵣ < 1; Cu, Bi, $H_{2}O$; repelled; T-independent
- Para: χ > 0 small; Al, $O_{2}$; attracted; χ = C/T
- Ferro: χ >> 0; Fe, Co, Ni; strongly attracted; domains; hysteresis
### KEY CONSTANTS
- μ_{0} = 4π × 10^{-7} T·m/A
- e = \$1.6 \times 10^{-1}$^{9} C; m_p = \$1.67 \times 10^{-2}$^{7} kg
### NEET MUST-REMEMBER
1. Magnetic force does NO work (F ⊥ v always)
2. T = 2πm/(qB) — velocity-independent
3. Ammeter = PARALLEL shunt (low R); Voltmeter = SERIES R (high R)
4. Solenoid B depends on n = N/L, not N alone
5. Above Curie temperature: ferromagnet → paramagnetic$
Part of MAG-01 — Magnetic Effects of Current & Magnetism
Exam Cheat Sheet — All Key Facts for NEET
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