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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
The Forces

Concepts Of Physics MCQ Edition [Volume 1] · Physics · The Forces

In a hydrogen atom's ground state, the average separation between...

In a hydrogen atom's ground state, the average separation between the proton and the electron is 5.3×10−11 m5.3 \times 10^{-11} \text{ m}. Determine the Coulomb force between them at this separation.

Options

  1. A4.3×10−18 N4.3 \times 10^{-18} \text{ N}
  2. B8.2×10−8 N8.2 \times 10^{-8} \text{ N}
  3. C2.1×10−8 N2.1 \times 10^{-8} \text{ N}
  4. D8.2×10−9 N8.2 \times 10^{-9} \text{ N}

Correct answer

B. 8.2×10−8 N8.2 \times 10^{-8} \text{ N}

Step-by-step solution

The Coulomb force between the proton and the electron is given by Coulomb's law:

F=14πϵ0q1q2r2F = \dfrac{1}{4 \pi \epsilon_0} \dfrac{q_1 q_2}{r^2}

Substituting the given values:

q1=e=1.6×10−19 Cq_1 = e = 1.6 \times 10^{-19} \text{ C}

q2=e=1.6×10−19 Cq_2 = e = 1.6 \times 10^{-19} \text{ C}

r=5.3×10−11 mr = 5.3 \times 10^{-11} \text{ m}

14πϵ0=9×109 N m2/C2\dfrac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \text{ N m}^2/\text{C}^2

F=9×109×(1.6×10−19)2(5.3×10−11)2F = \dfrac{9 \times 10^9 \times (1.6 \times 10^{-19})^2}{(5.3 \times 10^{-11})^2}

F=9×109×2.56×10−3828.09×10−22F = \dfrac{9 \times 10^9 \times 2.56 \times 10^{-38}}{28.09 \times 10^{-22}}

F=23.04×10−2928.09×10−22F = \dfrac{23.04 \times 10^{-29}}{28.09 \times 10^{-22}}

F≈0.82×10−7 NF \approx 0.82 \times 10^{-7} \text{ N}

F=8.2×10−8 NF = 8.2 \times 10^{-8} \text{ N}
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