📚 Learning Guide
Electric Field Effects on Charge
easy

If a spherical surface encloses a uniformly charged sphere, how does the electric field behave at points outside the sphere according to Gauss's Law?

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Choose the Best Answer

A

The electric field behaves as if all the charge were concentrated at the center of the sphere.

B

The electric field is zero at all points outside the sphere.

C

The electric field decreases exponentially with distance from the sphere.

D

The electric field is constant at all points outside the sphere.

Understanding the Answer

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Answer

When the Gaussian surface lies outside the uniformly charged sphere, Gauss’s Law tells us that the total electric flux through the surface depends only on the total charge inside, not on how that charge is distributed. Because the sphere is uniformly charged, the charge inside the surface can be treated as if it were all concentrated at the sphere’s center. The symmetry of a sphere then forces the electric field to be radial and have the same magnitude at every point on the Gaussian surface. Using the relation \(E \cdot 4\pi r^{2} = Q/\varepsilon_{0}\), the field at a distance \(r\) from the center is \(E = \frac{1}{4\pi\varepsilon_{0}}\frac{Q}{r^{2}}\), pointing outward. For example, if the sphere carries a charge of \(1\,\mu\text{C}\) and you measure the field at twice the sphere’s radius, the field will be one fourth of its value at the sphere’s surface, just as for a point charge.

Detailed Explanation

Gauss's Law tells us that for a sphere with uniform charge, the electric field outside behaves like the field of a single point charge at the center. Other options are incorrect because Some think the field vanishes because charges inside cancel; People sometimes believe the field drops exponentially.

Key Concepts

Gauss's Law
Topic

Electric Field Effects on Charge

Difficulty

easy level question

Cognitive Level

understand

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