# Electric fields and dry air

• Jodi
In summary, the conversation is about a question regarding the amount of charge that can be packed onto a green pea before it spontaneously discharges due to a high electric field. The formula used is E=kq/r^2 and the answer given is 5.0E-9 C, but it is believed to be incorrect. The person is advised to check their math and units, as they are on the right track.

#### Jodi

Hi; Could somebody please help me with the following question: Dry air will break down and generate a spark if the electric field exceeds about 2.90E+6 N/C. How much charge could be packed onto a green pea (diameter 0.800 cm) before the pea spontaneously discharges?
The formula i used was E=kq/r^2. And the answer i got was 5.0E-9 C. But that answer is not correct, does anyone know what I am doing wrong? Thanks.

Jodi said:
Hi; Could somebody please help me with the following question: Dry air will break down and generate a spark if the electric field exceeds about 2.90E+6 N/C. How much charge could be packed onto a green pea (diameter 0.800 cm) before the pea spontaneously discharges?
The formula i used was E=kq/r^2. And the answer i got was 5.0E-9 C. But that answer is not correct, does anyone know what I am doing wrong? Thanks.

Check your math and your units. You are doing the right thing.

Hi there,

Based on the information provided, it is not entirely clear what formula you used to calculate the charge on the green pea. However, I can offer some clarification and a potential solution.

Firstly, the formula you mentioned, E=kq/r^2, is correct for calculating the electric field strength at a given distance from a point charge. However, this formula does not directly relate to the question at hand, which asks about the charge that can be packed onto the green pea before it discharges.

To answer this question, we can use the concept of electric breakdown voltage. This is the minimum electric field strength required for a material to break down and conduct electricity. In the case of dry air, this breakdown voltage is approximately 2.90E+6 N/C, as stated in the question.

Now, the question asks for the maximum charge that can be packed onto a green pea before it discharges. In other words, we need to find the maximum charge that can be packed onto the pea while keeping the electric field strength below the breakdown voltage of 2.90E+6 N/C.

To do this, we can rearrange the formula for electric field strength to solve for charge, giving us q = Er^2/k. Plugging in the values given in the question (E = 2.90E+6 N/C, r = 0.800 cm, and k = 8.99E+9 Nm^2/C^2), we get q = (2.90E+6 N/C)(0.008 m)^2 / (8.99E+9 Nm^2/C^2) = 2.57E-11 C.

This means that the maximum charge that can be packed onto the green pea without causing it to spontaneously discharge is 2.57E-11 C. This is significantly smaller than the answer you obtained, which suggests that your calculation may have been incorrect. I would recommend double-checking your calculations and units to ensure accuracy.

I hope this helps! Let me know if you have any further questions.

## 1. What is an electric field?

An electric field is a physical phenomenon that is created by the presence of electrically charged particles. It is a region in space where electrically charged objects experience a force, either attracting or repelling each other.

## 2. How is an electric field created in dry air?

An electric field in dry air is created when there is a difference in electric charge between two objects. This can occur naturally through processes such as lightning or it can be artificially created using devices such as generators or batteries.

## 3. Can an electric field exist in a vacuum or does it require a medium like air?

An electric field can exist in a vacuum as it is a fundamental force of nature that does not require a medium to propagate. However, the presence of a medium such as dry air can affect the strength and behavior of the electric field.

## 4. What are the effects of electric fields in dry air on living organisms?

Electric fields in dry air can have both positive and negative effects on living organisms. Small amounts of electric fields may have beneficial effects, such as aiding in nerve and muscle function. However, high levels of electric fields can be harmful, causing electric shock or disrupting the body's natural electric signals.

## 5. How are electric fields in dry air measured?

Electric fields in dry air can be measured using devices called voltmeters or electromagnetic field (EMF) meters. These devices detect the strength and direction of the electric field and display it in units of volts per meter (V/m).