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Other Charge Distributions - Fields & Potentials

Hannah Baker

Hannah Baker

8 min read

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Study Guide Overview

This study guide covers advanced applications of charge distributions, Gauss' Law, and electric potential. It examines extended charge distributions (lines, rings, sheets) and how to calculate their electric fields and potentials using integration. It reviews applying Gauss' Law to various shapes like spheres, cylinders, and sheets to determine electric fields. Finally, it discusses calculating potential differences for various charge configurations, including lines and conducting sheets.

Advanced Applications of Charge Distributions, Gauss' Law, and Electric Potential

This section dives into more complex scenarios involving charge distributions, Gauss' Law, and electric potential calculations. It builds upon the foundational concepts covered earlier, so make sure you're comfortable with those before proceeding. Let's get started! 🚀

Extended Charge Distributions

So far, we've treated charged objects as point charges. Now, we'll tackle situations where charge is spread out over a line, ring, or sheet. The key idea is to break down the total charge Q into tiny pieces dq, each contributing a small electric field dE. Then, we integrate to find the total field E. Here's the general formula:

dE=kdqr2r^dE = k \frac{dq}{r^2} \hat{r}

where r is the radius vector.

Ring of Charge Example

Ring of Charge
Ring of Charge Equation
Ring of Charge Approximation

If x >>> a, the equation simplifies to that of a point charge, which is a great way to check your work.

Line of Charge Example

Line of Charge

First, express dq in terms of dy using the linear charge density λ:

Line of Charge dq

Then, integrate to find the total electric field, using the Pythagorean theorem to find r:

Line of Charge Integration
Key Concept

Remember that the key to solving these problems is to break the charge distribution into small pieces (dq), find the field due to each piece (dE), and then integrate to find the total field.

Gauss' Law for Various Shapes

Gauss' Law is your best friend for finding electric fields due to symmetrical charge distributions. Here's a quick rundown of how to apply it to different...

Question 1 of 12

What is the magnitude of the electric field dEdE due to a small charge dqdq at a distance rr?

kdqrk \frac{dq}{r}

kdqr2k \frac{dq}{r^2}

kdq2r2k \frac{dq^2}{r^2}

kr2dqk \frac{r^2}{dq}