15. Positive charge Q is placed on a conducting spherical shell with inner radius \( R_1 \) and outer radius \( R_2 \). A point charge q is placed at the center of the cavity. The magnitude of the electric field at a point outside the shell, a distance r from the center, is(A)\( Q / 4\pi\varepsilon_0 R_2^2 \)(B)\( Q / 4\pi\varepsilon_0 (R_2^2 - r^2) \)(C)\( q / 4\pi\varepsilon_0 r^2 \)(D)\( (q+Q) / 4\pi\varepsilon_0 r^2 \)(E)\( (q+Q) / 4\pi\varepsilon_0 (R_2^2 - r^2) \)

7. The relation PV = nRT holds for all ideal gases. The additional relation \( PV^\gamma \) holds for an adiabatic process. The figure below shows two curves: one is an adiabat and one is an isotherm. Each starts at the same pressure and volume. Which statement is correct? (Note: "∝" means "is proportional to".)(A)Isotherm: \( P \propto \frac{1}{V} \); Adiabat: \( P \propto \frac{1}{V^\gamma} \): A is both an isotherm and an adiabat.(B)Isotherm: \( P \propto \frac{1}{V^\gamma} \); Adiabat: \( P \propto \frac{1}{V} \): B is an isotherm, A is an adiabat.(C)Isotherm: \( P \propto \frac{1}{V} \); Adiabat: \( P \propto \frac{1}{V^\gamma} \): A is an isotherm, B is an adiabat.(D)Isotherm: \( P \propto \frac{1}{V^\gamma} \); Adiabat: \( P \propto \frac{1}{V} \): B is both an isotherm and an adiabat.(E)I cannot answer this without additional information about the starting temperature.

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