# Answer to Question #45715 in Electromagnetism for victor

Question #45715

The outer surface of the cardboard center of a paper towel roll:

is a possible Gaussian surface

cannot be a Gaussian surface because it encloses no charge

cannot be a Gaussian surface since it is an insulator

cannot be a Gaussian surface because it is not a closed surface

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is a possible Gaussian surface

cannot be a Gaussian surface because it encloses no charge

cannot be a Gaussian surface since it is an insulator

cannot be a Gaussian surface because it is not a closed surface

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Expert's answer

For a Gaussian law suits any closed surface.

In this case with assuming that paper towel roll is not closed surfacethe last option is correct :

In this case with assuming that paper towel roll is not closed surfacethe last option is correct :

**cannot be a Gaussian surface because it is not a closed surface**
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