17. A charge of +3.0 μC is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25 μC from infinity to the center of the circle? (A)5.4 J (B)3.4 J (C)4.3 J (D)2.7 J (E)6.8 J

3. A spherical shell has inner radius R₁, outer radius R₂, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point particle of mass m located a distance d from the center, outside the inner radius and inside the outer radius, is: (A)0 (B)GMm/d² (C)GMm/(R₂²-R₁³) (D)GMm(d³-R₁³)/d²(R₂³-R₁³) (E)GMm/(d²-R₁²)

17. A charge of +3.0 μC is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25 μC from infinity to the center of the circle?
(A)5.4 J
(B)3.4 J
(C)4.3 J
(D)2.7 J
(E)6.8 J

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