Finding an electric field from a scalar field

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To find the scalar field that produces the given electric field E, one must integrate each component of E while considering arbitrary functions of the other variables. The integration of the x-component suggests a form for the scalar potential V, which includes an arbitrary function f(y,z) due to the partial derivative with respect to x. The key is to use the other components of E to determine the form of f by ensuring consistency with their respective partial derivatives. It's important to remember that each component of the electric field corresponds to the negative gradient of the scalar potential. The process involves careful integration and consideration of the relationships between the variables to fully define the scalar field.
Noone1982
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Say I know an electric field

E = (yz - 2x)x-hat + (xz)y-hat + (xy)z-hat

How do I find the scalar field that would produce that? If I integrate each part I get

Vx = xyz - x^2
Vy = xyz
Vz = xyz

Vt = 3xy - x^2

To find E, I would take E = gradient cross the scalar field, but that would clearly not work. What I am doing wrong?
 
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Pick any component you want and integrate. For instance, if you picked the x-component then your guess "answer" would look like V = xyz - x^2 + f(y,z), where f is an arbitrary function of y and z. This is because you only know that the partial derivative of V with respect to x is equal to yz - 2x. To figure out what your function f is, make use of your information about the other two partial derivatives of V. Of course, V is still undefined up to a constant.
 
Each component of the E-Field is the (-) derivitive of the scalar potential with THAT coordinate , yes E is the (-) gradient .

Notice that d(x^2)/dy = 0 , so that E_y cannot give info about purely "x" terms in V, (or x and z terms, either). Similarly, E_x gives no info about purely y or z terms.

Don't add the xyz terms, just make sure they all agree.
 
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Im still fuzzy on how to obtain the unknown function. Can you further explain?
 
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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