4. An isolated charged capacitor of capacitance C0 has horizontal plates. A dielectric of dielectric constant K is inserted such that the capacitor is filled with the dielectric material. What is the resulting capacitance? (A) C0 (B) C0/K (C) KC0 (D) (K−1)C0

10. The number of collisions a molecule makes per second is called collision frequency. At one atmosphere and 0 °C, estimate the collision frequency of air molecules. [The diameter of an air molecule under one atmosphere and 0 °C is approximately 3×10⁻¹⁰ (m), the average molecular speed is approximately 460 (m/s), and the molecular number density is approximately 2.7×10²⁵ molecules/m³]. (A) 3.5×10⁵ (collisions/s) (B) 3.5×10⁷ (collisions/s) (C) 3.5×10⁹ (collisions/s) (D) 3.5×10¹¹ (collisions/s)

4. An isolated charged capacitor of capacitance C₀ has horizontal plates. A dielectric of dielectric constant K is inserted such that the capacitor is filled with the dielectric material. What is the resulting capacitance?
(A) C₀
(B) C₀/K
(C) KC₀
(D) (K−1)C₀

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