# Understanding E-Field Equations and Notation in Electronic Engineering

• charlotty
In summary, the conversation is about a boyfriend who is studying electronic engineering and is stuck on a difficult equation involving the total electric field and notation he does not understand. The person asking for help has a law degree and may not fully understand the problem, but is trying to assist. The conversation also includes a discussion on how to properly display equations with symbols.
charlotty
ive already posted this is another bit of the forums, and only just noticed the Electronic Engineering section!

My boyfriend is doing a dgree in electronic engineering and is studying fields and devices at the moment and is really stuck so i was wondering if anyone could help!

His notes say "the total e field is the vector sum over all the N charges. If we line up our axes so that the charges are on the x-axis then we get..."
a really long equation. (i would write it here, but there's no way to get all the equations symbols!)

THe equation has a x' in it, and he has no idea what the notation means.

im probably not making any sense to anyone, but i just wanted to see if i could help him (im studying for a law degree so this is all spanish to me!)

thanks so much,

charlotty

charlotty said:
ive already posted this is another bit of the forums, and only just noticed the Electronic Engineering section!

My boyfriend is doing a dgree in electronic engineering and is studying fields and devices at the moment and is really stuck so i was wondering if anyone could help!

His notes say "the total e field is the vector sum over all the N charges. If we line up our axes so that the charges are on the x-axis then we get..."
a really long equation. (i would write it here, but there's no way to get all the equations symbols!)

THe equation has a x' in it, and he has no idea what the notation means.

im probably not making any sense to anyone, but i just wanted to see if i could help him (im studying for a law degree so this is all spanish to me!)

thanks so much,

charlotty

Actually there is a way to get all of those crazy symbols. Here is an example,

$$\oint_S \vec E \cdot d\vec S = \frac{Q_{enc}}{\epsilon_0}$$

There is a lot of symmetry in your problem, how are you going about solving it?

EDIT:
I just noticed that you did not say an infinite rod. So my symmetry comment above is misleading. Instead you will need to sum of differential elements of voltage or electric fields.

$$V = \frac{1}{4 \pi \epsilon_0} \int_{V'} \frac{\rho}{R} \, dv'$$

Last edited:
Also, the notation $x'$ is usually used to denote a variable corresponding to a source point. IE, the vector $\vec r'$ would point to the location of a point charge.

Last edited:

## 1. How does the electric field from a charged rod change with distance?

The electric field from a charged rod follows an inverse square law, meaning that it decreases with distance from the rod. As distance increases, the electric field strength decreases proportionally to the square of the distance.

## 2. What is the direction of the electric field from a charged rod?

The electric field from a charged rod points away from the positively charged end and towards the negatively charged end. This is because electric fields always point in the direction of the force that a positive test charge would experience if placed in the field.

## 3. How does the electric field from a charged rod change with the amount of charge on the rod?

The electric field from a charged rod is directly proportional to the amount of charge on the rod. This means that if the charge on the rod is doubled, the electric field strength will also double.

## 4. Why does the electric field from a charged rod become weaker with distance?

The electric field from a charged rod becomes weaker with distance because the electric field lines spread out as they move away from the rod. This means that the same amount of electric field is spread out over a larger area, resulting in a weaker electric field strength at a greater distance.

## 5. Can the electric field from a charged rod be manipulated?

Yes, the electric field from a charged rod can be manipulated by changing the amount of charge on the rod or by changing the distance from the rod. Additionally, other charged objects in the vicinity can also affect the electric field from a charged rod through the principles of superposition.

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