Thick wire: B inside and outside (Ampère’s law)मोटा तार: अंदर और बाहर B (ऐम्पियर नियम)Thick wire: B inside and outside (Ampère’s law)

NCERT Fig 4.13–4.14 · Class 12 Physics · Chapter 4 · interactive diagram

Parts and what they mean

• Cross-section of a long wire (radius a) (लंबे तार का अनुप्रस्थ काट (त्रिज्या a)) — Current I out of the page, spread uniformly over the area.
• Amperian loop 1 (r < a) (ऐम्पियरी लूप 1 (r < a)) — Encloses only part of the current: Ie = I r²/a².
• Amperian loop 2 (r > a) (ऐम्पियरी लूप 2 (r > a)) — Encloses the full current I.
• Radius a of the wire (तार की त्रिज्या a) — Boundary between “inside” and “outside”.
• Graph of B against r (B और r का ग्राफ़) — Rises linearly to a peak at the surface, then falls as 1/r.
• Maximum at r = a (r = a पर अधिकतम) — B is largest at the surface of the wire: μ₀I/2πa.
• Inside: B ∝ r (अंदर: B ∝ r) — B = (μ₀I/2πa²) r.
• Outside: B ∝ 1/r (बाहर: B ∝ 1/r) — B = μ₀I/2πr, as for a thin wire.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 4.13–4.14. Report a mistake