Physics · Electromagnetic Induction · NEET
The Φ is the flux through ONE single turn. The total flux linked with the whole coil is N × Φ, called the flux linkage. So the correct form is L = (NΦ)/I. In NEET problems the value given as 'flux linked with each turn' is per turn, so you must multiply by N before dividing by I. Skipping the N is the number one mistake.
Each of the N turns sees the same flux Φ. Because the turns are in series, their contributions add up, so the coil links a total flux of NΦ. Self-inductance measures total flux linkage per unit current, so we use NΦ, not just Φ.
Flux per turn (Φ) is what passes through one loop, measured in weber (Wb). Flux linkage (NΦ) is the total for all N turns, measured in weber-turns. L = flux linkage / current = NΦ/I. Always identify which one the question gives you.
No. Even though the formula has I in it, L is a fixed property of the coil. It depends only on geometry (number of turns, area, length) and the core material. If you double I, the flux Φ also doubles, so NΦ/I stays the same. L is constant for a given coil.
L is in henry (H), Φ is in weber (Wb), I is in ampere (A). So 1 H = 1 Wb/A = 1 Wb·turn per ampere. If you get an odd number, check that flux is in Wb and current in A (convert mA and mWb first).
A long solenoid has 1000 turns. When a current of 4 A flows through it, the magnetic flux linked with each turn of the solenoid is 4 × 10⁻³ Wb. The self-inductance of the solenoid is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
L = NΦ/I, where N is the number of turns, Φ is the magnetic flux through one turn, and I is the current. The product NΦ is the flux linkage.
The henry (H). One henry equals one weber-turn per ampere: 1 H = 1 Wb/A.
Because you must multiply the per-turn flux (4×10⁻³ Wb) by N = 1000 turns before dividing by I = 4 A. That gives 4/4 = 1 H. Dropping the 1000 turns wrongly gives 1 mH.
Yes. L = NΦ/I is the general definition of self-inductance for any coil. The solenoid formula L = μ₀n²Al is just this general formula worked out for a long solenoid's geometry.
When I increases, the flux Φ increases in exact proportion (Φ ∝ I). So the ratio NΦ/I stays fixed. L depends only on the coil's shape, turns, and core, not on how much current flows.
