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#high temperature

6 public questions tagged with this topic.

Nuclear Reactions - Fission, Fusion and Energy Release

What is the role of high temperature in nuclear fusion?

**Nuclear fusion** source of energy in Sun, proton-proton cycle 4p→He+2e⁺+2ν+26.7 MeV, high temperature ~10⁷ K needed to give kinetic energy to overcome repulsion, thermal motion at high T allows tunneling, energy release because He BE/A higher than H. Fission releases energy because heavy nucleus BE/A ~7.6 MeV splits to intermediate ~8.5 MeV. High temperatures provide nuclei with sufficient kinetic energy to overcome the Coulomb barrier (electrostatic repulsion), allowing them to come close enough for the nuclear force to cause fusion. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀

Ref: NCERT > Physics Book > Atoms and Nuclei > Nuclear Reactions - Fission, Fusion and Energy Release

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Hydrogen Atom Properties - Radius, Speed and Energy

Why does nuclear fusion require extremely high temperatures?

**Hydrogen atom radius** r_n = n² a₀, a₀=5.3×10⁻¹¹ m first Bohr radius, r₂=4a₀=2.12×10⁻¹⁰ m, ratio r₄/r₂ =16/4=4, r₃=9a₀, circumference 2πr_n =2π n² a₀, for n=3 circumference=2π×9×5.3×10⁻¹¹=3×10⁻⁹ m. Orbital period T =2πr/v, v_n = v₁/n, v₁=2.2×10⁶ m/s, T₂=2πr₂/v₂, v₂=1.1×10⁶ m/s, T₂≈1.21×10⁻¹⁵ s. High temperatures provide nuclei with enough kinetic energy to overcome the electrostatic repulsion (Coulomb barrier) between positively charged nuclei, enabling fusion via the nuclear force. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.5 MeV, evaluation yie

Ref: NCERT > Physics Book > Atoms and Nuclei > Hydrogen Atom Properties - Radius, Speed and Energy

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Hydrogen Atom Properties - Radius, Speed and Energy

What is the key requirement for nuclei to undergo fusion?

**Energy in hydrogen** total E_n = -13.6/n² eV, kinetic K = +13.6/n² eV, potential U = -27.2/n² eV, ratio K/U = -1/2, total negative indicates bound, zero at ionization, negative total means electron bound, requires energy to free. For n=4 E=-0.85 eV, U=-1.7 eV, K=0.85 eV, potential energy twice total negative. Fusion requires nuclei to overcome the Coulomb barrier (electrostatic repulsion between positively charged nuclei), which is achieved by providing high kinetic energy through elevated temperatures. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u = 931.

Ref: NCERT > Physics Book > Atoms and Nuclei > Hydrogen Atom Properties - Radius, Speed and Energy

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PHYSICS

Why does nuclear fusion require extremely high temperatures?

High temperatures provide nuclei with enough kinetic energy to overcome the electrostatic repulsion (Coulomb barrier) between positively charged nuclei, enabling fusion via the nuclear force.

Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27), Chapter: Kinetic Theory (Latest NCERT 2026-27), Topic: RMS speed v_rms ∝ √T, temperature dependence, ratio v₂/v₁ = √(T₂/T₁) and calculation

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Properties of Plasma Membrane

What happens when cholesterol is added to a membrane at high temperature?

Dual effect of cholesterol on membrane order described as condensing and fluidity buffering arises from rigid steroid ring system intercalating among phospholipid acyl chains. At temperatures above phospholipid Tm chains highly disordered with many gauche conformers large area per lipid fluid low order. Cholesterol hydroxyl moiety positioned near phospholipid carbonyl oxygen forms hydrogen bond, rigid tetracyclic rings restrict chain isomerization reducing number gauche kinks order parameter S increases from zero point two to zero point five measured deuterium NMR, lateral diffusion coefficien

Ref: Ohvo-Rekila et al., Cholesterol Interactions and Membrane Fluidity Biphasic Effect, Prog Lipid Res 2002.

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