Questions
Question 1
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What does electric flux measure for a surface in an electric field?
Question 2
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What is the direction of the area vector for a flat surface?
Question 3
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Write the flux through a flat surface in a uniform electric field in terms of \(E\), \(A\), and \(\theta\).
Question 4
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A \(60\,\mathrm{N\,C^{-1}}\) uniform electric field is perpendicular to a \(0.40\,\mathrm{m^2}\) surface and points with the chosen area vector. Find \(\Phi_E\).
Question 5
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A uniform electric field is parallel to a flat surface. What is the electric flux through the surface?
Question 6
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A \(120\,\mathrm{N\,C^{-1}}\) field makes a \(60^\circ\) angle with the area vector of a \(0.50\,\mathrm{m^2}\) surface. Find the flux.
Question 7
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A \(90\,\mathrm{N\,C^{-1}}\) field points opposite the area vector of a \(0.20\,\mathrm{m^2}\) flat surface. Find the flux.
Question 8
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A flat surface has area vector \(\vec A=(0.30\,\mathrm{m^2})\hat\imath\). A uniform field is \(\vec E=(50\,\mathrm{N\,C^{-1}})\hat\imath\). Find \(\Phi_E\).
Question 9
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A flat surface has \(\vec A=(0.20\hat\imath+0.10\hat\jmath)\,\mathrm{m^2}\) and \(\vec E=(40\hat\imath-30\hat\jmath)\,\mathrm{N\,C^{-1}}\). Find the flux.
Question 10
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A circular plate of radius \(0.15\,\mathrm{m}\) has its area vector \(35^\circ\) from a \(200\,\mathrm{N\,C^{-1}}\) uniform field. Find the flux.
Question 11
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A square loop of side \(0.30\,\mathrm{m}\) is rotated from having its area vector parallel to a uniform field to having its area vector perpendicular to the field. If \(E=75\,\mathrm{N\,C^{-1}}\), what is the change in flux?
Question 12
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A \(0.10\,\mathrm{m^2}\) surface has flux \(4.0\,\mathrm{N\,m^2\,C^{-1}}\) in a \(100\,\mathrm{N\,C^{-1}}\) uniform field. What angle does the field make with the area vector?
Question 13
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A uniform field \(\vec E=E\hat\imath\) passes through a cube of side \(L\). Find the flux through the right face, left face, and the total flux through the closed cube.
Question 14
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A uniform electric field points upward through a horizontal disk. Compare the flux if the disk's area vector is chosen upward versus downward.
Question 15
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A flat rectangular surface has side lengths \(a\) and \(b\). Its normal is tilted by angle \(\theta\) from a uniform field \(\vec E\). Derive the flux and state when its magnitude is largest.
Question 16
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A curved surface is divided into small patches. Explain why the flux is \(\int_S \vec E\cdot d\vec A\), not simply \(EA\).
Question 17
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A closed box is placed in a uniform electric field. Without using Gauss's law, argue from area vectors why the total flux through the box is zero.
Question 18
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A flat surface has fixed area \(A\) in a uniform field \(E\). You may choose its orientation. Derive the range of possible flux values and explain the geometric meaning of the endpoints.
Question 19
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Two flat surfaces have the same boundary curve but one is bulged outward. In a uniform electric field, explain why their fluxes need not be the same if the boundary is not closed by an additional surface.
Question 20
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A surface is made from many small flat patches with area vectors \(\Delta\vec A_i\). Starting from the uniform-field dot product, derive the surface-integral definition of electric flux and state the assumptions needed for the limiting process.