Example 5.2: which positions are in equilibrium?उदाहरण 5.2: कौन-सी स्थितियाँ संतुलन में हैं?Example 5.2: which positions are in equilibrium?

NCERT Fig 5.4 · Class 12 Physics · Chapter 5 · interactive diagram

Parts and what they mean

• Needle P at O (moment upward) (O पर सुई P (आघूर्ण ऊपर)) — Its axis is vertical, so Q4 and Q6 are on its axis and Q1, Q2, Q3, Q5 are on its normal bisector.
• Q1 — not in equilibrium (Q1 — संतुलन में नहीं) — On the bisector P’s field points down; m_Q points sideways (perpendicular) → torque acts.
• Q2 — not in equilibrium (Q2 — संतुलन में नहीं) — Same reason as Q1: m_Q ⟂ B_P.
• Q3 — stable (Q3 — स्थायी) — On the bisector B_P points opposite to m_P (down); m_Q also points down → parallel → stable.
• Q4 — unstable (Q4 — अस्थायी) — On the axis B_P points along m_P (up); m_Q points down → anti-parallel → unstable.
• Q5 — unstable (Q5 — अस्थायी) — On the bisector B_P points down; m_Q points up → anti-parallel → unstable.
• Q6 — stable, lowest energy (Q6 — स्थायी, न्यूनतम ऊर्जा) — On the axis B_P is up and twice as strong as on the bisector; m_Q is up → U = −2(μ₀/4π)m²/r³, the lowest of all.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 5.4. Report a mistake