How Does Changing a Gaussian Surface's Shape Affect Net Flux?

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The net flux through a Gaussian surface is determined solely by the enclosed charge, according to Gauss' Law. When a spherical Gaussian surface is replaced by a cube of the same volume, or a cube with one third the volume, the net flux remains unchanged. This is because the electric field lines are spherically symmetric around the positive test charge, ensuring that the flux through any closed surface is consistent. The direction and magnitude of the electric field are uniform at any point on the surface, regardless of its shape. Thus, changing the shape of the Gaussian surface does not affect the net flux.
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A positive test charge is placed at the center of a spherical Gaussian surface. What happens to the net flux through the Gaussian surface when the surface is replaced by a cube of the same volume whose center is at the same point? or When the sphere is replaced by a cube of one third the volume centered at the same point?
 
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See Gauss' Law. Net flux through ANY closed surface depends only on...
 


The net flux through the Gaussian surface will remain the same in both cases. This is because the electric field lines passing through the center of the spherical Gaussian surface will also pass through the center of the cube, regardless of its volume. This is due to the fact that the electric field is spherically symmetric around the positive test charge, meaning the direction and magnitude of the field will be the same at any point along the surface, regardless of its shape. Therefore, the net flux through the Gaussian surface will not change when it is replaced by a cube of the same volume or a cube with one third the volume.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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