# Griffith's Figure 2.24: E-Fields Canceling, Not 0?

• ehrenfest
In summary, the E-fields in regions i and iii cancel completely if assuming infinite plates, but in real life they do not cancel completely. This is because equation 2.17 states that the E-field is independent of the distance from the plates, a property of infinite surface charge distributions.
ehrenfest
[SOLVED] Griffith's Figure 2.24

## Homework Statement

This question refers to Griffith's E and M book.

In the paragraph above this figure, Griffith's says that the E-fields cancel in regions i and iii. He does NOT mean cancel completely, correct? That is, the field is NOT 0 in those two regions, correct?

ehrenfest said:

## Homework Statement

This question refers to Griffith's E and M book.

In the paragraph above this figure, Griffith's says that the E-fields cancel in regions i and iii. He does NOT mean cancel completely, correct? That is, the field is NOT 0 in those two regions, correct?

## The Attempt at a Solution

Yes they cancel completely if you assume infinite plates. Of course in real life there are no infinite plates.

Oh I see. It is because equation 2.17 tells us that the E-field is independent of the distance from the plates.

ehrenfest said:
Oh I see. It is because equation 2.17 tells us that the E-field is independent of the distance from the plates.

Exactly. This is the special property of an infinite surface charge distribution.

A point charge has an E field that goes like 1/r^2. A uniform line of charge (infinite) has an E field going like 1/r. A uniform infinite surface charge distribution has a constant E field

## What is Griffith's Figure 2.24?

Griffith's Figure 2.24 is a diagram in the textbook "Introduction to Electrodynamics" by David J. Griffiths, which demonstrates the concept of electric fields canceling out to create an overall field of zero.

## What does E-Fields Canceling, Not 0 mean?

This phrase refers to the idea that while the individual electric fields may cancel out, the overall electric field does not become zero. Instead, it becomes a more complex and non-uniform field.

## Why is this concept important?

This concept is important because it demonstrates how electric fields interact and combine with one another, and how they can create a more complex and varied overall field. It also helps to explain phenomena such as interference and diffraction.

## How does Griffith's Figure 2.24 illustrate this concept?

The figure shows two point charges with opposite signs, creating two individual electric fields that cancel each other out at certain points. However, the overall field is not zero and is instead a combination of the two individual fields.

## How does this concept relate to real-life situations?

This concept is relevant in many real-life situations, such as in electrical engineering, optics, and even in understanding the behavior of atoms and molecules. It helps to explain how fields interact and combine in complex systems.

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