Question

# Three glass fishbowls are at rest on a horizontal surface. The fishbowls are identical in shape...

Three glass fishbowls are at rest on a horizontal surface. The fishbowls are identical in shape and volume, and each has a circular opening of the same area A. The fishbowls differ, however, in the location of the opening. A uniform magnetic field, directed downward, is applied to the bowls. Through which fishbowl, if any, is the magnitude of the magnetic flux greatest through the glass?

A. a fishbowl with an opening on one side that is oriented 45° to the horizontal

B. a fishbowl with an opening on one side that is oriented vertically

C. none of the fishbowls (The magnetic flux is equal in all three fishbowls.)

D. a fishbowl with an opening on a flat top that is parallel to the horizontal

The magnetic flux is a measure of the no of field lines passing through the area of the substance. Here, the flux is asked through the glass. So, the maximum flux passes through the glass when the area of the surface perpendicular to the magnetic field is maximum.

In other words, the area of the hole as viewed normal to the field should be minimum.

This area is minimum when the field and the area vector are perpendicular to each other.

Remember that the area vector is perpendicular to the area.

Thus, the area of the hole must be parallel to the magnetic field.

Si,ce the magnetic field is directed downward, the area of the hole must be parallel to the vertical plane, so that minimum flux passes through the hole and maximum flux passes through the glass.

So, the correct answer is option B

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