Question

Difficulty: Very hardFundamental and Derived Units

Match each physical quantity listed on the left with its corresponding SI unit expressed strictly in terms of fundamental (base) units on the right.

  • Electric permittivity of free space (ε0\varepsilon_0)kg−1⋅m−3⋅s4⋅A2\text{kg}^{-1}\cdot\text{m}^{-3}\cdot\text{s}^4\cdot\text{A}^2
  • Magnetic permeability of free space (μ0\mu_0)kg⋅m⋅s−2⋅A−2\text{kg}\cdot\text{m}\cdot\text{s}^{-2}\cdot\text{A}^{-2}
  • Thermal conductivity (kk)kg⋅m⋅s−3⋅K−1\text{kg}\cdot\text{m}\cdot\text{s}^{-3}\cdot\text{K}^{-1}
  • Specific heat capacity (cc)m2⋅s−2⋅K−1\text{m}^2\cdot\text{s}^{-2}\cdot\text{K}^{-1}

Answer

Electric permittivity of free space maps to kg−1⋅m−3⋅s4⋅A2\text{kg}^{-1}\cdot\text{m}^{-3}\cdot\text{s}^4\cdot\text{A}^2, Magnetic permeability of free space maps to kg⋅m⋅s−2⋅A−2\text{kg}\cdot\text{m}\cdot\text{s}^{-2}\cdot\text{A}^{-2}, Thermal conductivity maps to kg⋅m⋅s−3⋅K−1\text{kg}\cdot\text{m}\cdot\text{s}^{-3}\cdot\text{K}^{-1}, and Specific heat capacity maps to m2⋅s−2⋅K−1\text{m}^2\cdot\text{s}^{-2}\cdot\text{K}^{-1}.
Each physical quantity is matched to its exact fundamental unit expression obtained by substituting basic formulas into SI base units (kg\text{kg}, m\text{m}, s\text{s}, A\text{A}, K\text{K}). Electric permittivity resolves to kg−1⋅m−3⋅s4⋅A2\text{kg}^{-1}\cdot\text{m}^{-3}\cdot\text{s}^4\cdot\text{A}^2, magnetic permeability resolves to kg⋅m⋅s−2⋅A−2\text{kg}\cdot\text{m}\cdot\text{s}^{-2}\cdot\text{A}^{-2}, thermal conductivity resolves to kg⋅m⋅s−3⋅K−1\text{kg}\cdot\text{m}\cdot\text{s}^{-3}\cdot\text{K}^{-1}, and specific heat capacity resolves to m2⋅s−2⋅K−1\text{m}^2\cdot\text{s}^{-2}\cdot\text{K}^{-1}.

Step-by-Step Solution

1
Derive the base SI units for Electric permittivity of free space (ε0\varepsilon_0).
From Coulomb's Law, F=q1q24πε0r2  ⟹  ε0=q1q24πFr2F = \frac{q_1 q_2}{4\pi \varepsilon_0 r^2} \implies \varepsilon_0 = \frac{q_1 q_2}{4\pi F r^2}. Expressing terms in SI fundamental units: charge q=A⋅sq = \text{A}\cdot\text{s}, force F=kg⋅m⋅s−2F = \text{kg}\cdot\text{m}\cdot\text{s}^{-2}, distance r=mr = \text{m}. Thus, [ε0]=(A⋅s)2(kg⋅m⋅s−2)⋅m2=kg−1⋅m−3⋅s4⋅A2[\varepsilon_0] = \frac{(\text{A}\cdot\text{s})^2}{(\text{kg}\cdot\text{m}\cdot\text{s}^{-2})\cdot\text{m}^2} = \text{kg}^{-1}\cdot\text{m}^{-3}\cdot\text{s}^4\cdot\text{A}^2.
Relating derived electromagnetic quantities to fundamental SI units via governing physical equations.
2
Derive the base SI units for Magnetic permeability of free space (μ0\mu_0).
From the force per unit length between parallel current-carrying conductors, FL=μ0I1I22πr  ⟹  μ0=2πFrI1I2L\frac{F}{L} = \frac{\mu_0 I_1 I_2}{2\pi r} \implies \mu_0 = \frac{2\pi F r}{I_1 I_2 L}. Units: [μ0]=(kg⋅m⋅s−2)⋅mA2⋅m=kg⋅m⋅s−2⋅A−2[\mu_0] = \frac{(\text{kg}\cdot\text{m}\cdot\text{s}^{-2})\cdot\text{m}}{\text{A}^2\cdot\text{m}} = \text{kg}\cdot\text{m}\cdot\text{s}^{-2}\cdot\text{A}^{-2}.
Using Ampère's force law to solve for magnetic permeability in base units.
3
Derive the base SI units for Thermal conductivity (kk).
From Fourier's Law of Heat Conduction, Qt=kAΔTΔx  ⟹  k=Q⋅ΔxtAΔT\frac{Q}{t} = k A \frac{\Delta T}{\Delta x} \implies k = \frac{Q \cdot \Delta x}{t A \Delta T}. Heat energy Q=kg⋅m2⋅s−2Q = \text{kg}\cdot\text{m}^2\cdot\text{s}^{-2}, time t=st = \text{s}, area A=m2A = \text{m}^2, thickness Δx=m\Delta x = \text{m}, temperature difference ΔT=K\Delta T = \text{K}. Thus, [k]=(kg⋅m2⋅s−2)⋅ms⋅m2⋅K=kg⋅m⋅s−3⋅K−1[k] = \frac{(\text{kg}\cdot\text{m}^2\cdot\text{s}^{-2})\cdot\text{m}}{\text{s}\cdot\text{m}^2\cdot\text{K}} = \text{kg}\cdot\text{m}\cdot\text{s}^{-3}\cdot\text{K}^{-1}.
Connecting thermal conduction equations to fundamental mechanics and thermodynamic units.
4
Derive the base SI units for Specific heat capacity (cc).
From Q=mcΔT  ⟹  c=QmΔTQ = m c \Delta T \implies c = \frac{Q}{m \Delta T}. Units: [c]=kg⋅m2⋅s−2kg⋅K=m2⋅s−2⋅K−1[c] = \frac{\text{kg}\cdot\text{m}^2\cdot\text{s}^{-2}}{\text{kg}\cdot\text{K}} = \text{m}^2\cdot\text{s}^{-2}\cdot\text{K}^{-1}.
Applying the defining equation of heat capacity to reduce the unit to fundamental base units.

Key Concept

Derivation of complex derived SI units from fundamental base units using fundamental physical laws.
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