# Calculating Electric Fields: Help

• Keegs32
In summary, to find the magnitude and direction of the electric field at the midpoint between an electron and a proton fixed at a separation distance of 925nm, you can use the equation E = Fe/q, where q represents the fundamental unit of charge. Since the electron and proton have equal and opposite charges, q can be substituted with 1.60E-19 Coulombs. The electric field of a dipole is not zero, and the electric fields of point charges superimpose, so using the point charge model can help solve this problem.

## Homework Statement

Question: An electron and a proton are fixed at a separation distance of 925nm. Find the magnitude and direction of the electric field at their midpoint.

E= Fe/q

## The Attempt at a Solution

(8.988 x 10^9) x (q/(9.25 x 10^-7)2)

This is the equation i have to solve for it but I don't know what q is in this situation. Help?

q in this case is the fundamental unit of charge. Both the electron and proton have the same magnitude of charge, but opposite. Since you're dealing with a single electron and proton, q is just 1.60E-19 Coulombs; sign depending on which particle you're examining.

But since they have equal and opposite charges, wouldn't that make q=0 which then makes the entire solution 0. Or does it have to do something with their midpoint in this problem?

These are non-moving point charges. There are a couple of other relationships that I might try to use to examine this scenario. One is the electric field of a point charge. The other is the forces between two charged particles separated by a distance r.

Try it. :-)

Last edited:
Keegs32 said:
But since they have equal and opposite charges, wouldn't that make q=0 which then makes the entire solution 0. Or does it have to do something with their midpoint in this problem?

q would only = 0 if the two particles were coincident. But to hopefully get you pointed in the right direction: the electric field of a dipole is not zero (except in the limit as r-->infinity.) Moreover, electric fields of point charges superimpose, just as forces do. So the pointcharge model--if you consider both the proton and the electron simultaneously--should get you there.

## 1. What is an electric field?

An electric field is a physical quantity that describes the strength and direction of the force experienced by a charged particle in the presence of other charged particles. It is represented by a vector at each point in space and is measured in units of Newtons per Coulomb (N/C).

## 2. How do you calculate the electric field?

The electric field at a point in space can be calculated by dividing the force exerted on a charged particle at that point by the charge of the particle. This is represented by the equation E = F/q, where E is the electric field, F is the force, and q is the charge of the particle.

## 3. What factors affect the strength of an electric field?

The strength of an electric field is affected by the magnitude of the charges involved and the distance between them. The closer the charges are, the stronger the electric field will be. Additionally, the type of material between the charges can also affect the strength of the electric field.

## 4. How do you represent an electric field graphically?

An electric field can be represented graphically using electric field lines. These lines show the direction and strength of the electric field at different points in space. The closer the lines are together, the stronger the electric field is at that point.

## 5. Can electric fields be shielded?

Yes, electric fields can be shielded by using materials that conduct electricity, such as metal. These materials can redirect the electric field, preventing it from reaching a certain area or object. This is why metal is often used in the construction of Faraday cages, which are used to block out external electric fields.