# Electric Fields and Parallel Plates

• DMac
In summary, the conversation is discussing the calculation of the final velocity of an electron passing through two parallel plates with different voltages. The questioner is unsure if they have enough information, but it is clarified that they only need the voltage between the first two plates. The formula for calculating the velocity is provided and confirmed to be correct, with the conversation then moving on to the next step in solving the problem.

#### DMac

I just want to know if I'm even given enough information in this question to generate an answer. I don't need an actual answer. Thanks.

"An electron is fired from a negative plate towards a hole in a positive plate. It then passes between two parallel plates that are 5 cm long and 3 cm apart with a voltage of 750 volts across them. If the accelerating voltage across the two original plates is 1200 volts what is the final velocity of the electron?"

From the first sentence of the question, it seems like I'm missing the distance between the plates, because with this distance I could calculate the electric field, and consequently continue solving the rest of the problem. Could I calculate it without this distance?

You are given the voltage between the first two plates. That's all you need.

OH! So I should calculate the velocity of the electron as such:

Delta E = q * Delta V
(This change in electric potential energy is all converted into kinetic energy.)

Using the mass of an electron,

.5 * m * v^2 = q * Delta V
v = sqrt[q * delta V * 2 / m]

I'm not sure if that's right.

That's the correct way to figure out the speed of the electron as it passes throught the hole. That's the first step.

Ah, I think I know where to go on from here. Thanks.

## 1. What is an electric field?

An electric field is a region in space where an electrically charged particle experiences a force. It is created by a source charge and can either attract or repel other charged particles.

## 2. How are electric fields and parallel plates related?

Electric fields and parallel plates are related because parallel plates are often used to create an electric field. When two parallel plates are charged with opposite charges, they create a uniform electric field between them.

## 3. How do you calculate the strength of an electric field between two parallel plates?

The strength of an electric field between two parallel plates can be calculated using the equation E = V/d, where E is the electric field strength, V is the potential difference between the plates, and d is the distance between the plates.

## 4. What is the purpose of using parallel plates to create an electric field?

The purpose of using parallel plates to create an electric field is to have a uniform and controllable field between the plates. This allows for easier manipulation and study of the electric field and its effects on charged particles.

## 5. How does the distance between parallel plates affect the strength of the electric field?

The distance between parallel plates has a direct relationship with the strength of the electric field. As the distance between the plates increases, the electric field strength decreases. This is because the electric field is spread out over a larger area, resulting in a weaker field.

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